Recently I filled up with cheaper fuel from Asda. At the present time it is giving me the lowest MPG I have ever had 45.5 on my Gen 2 T spirit. Maybe it is the colder weather only +3 today. Does any other Prius owner experience lower MPG with cheaper super market fuels?
With my Avensis I was told by the dealer it is OK to use the cheap fuels but every so often put the very best fuel you can in the tank. When I purchased the Prius dealer said just use any low octane fuel. ???
Full Version: Super Market Fuel
If anything the cold weather will improve the efficiency of combustion because of the higher density of oxygen, which will then give better fuel economy. Supermarket fuels are cheap because they are simply not as good as other fuels provided by brand-name companies. They aren't as refined and are always cheaper for a reason. 
With the Prius, it isn't meant for performance but then again, a cleaner and more powerful fuel makes for better combustion. I'd go for mid-range fuel on a prius it being a hybrid and all, but with anything else I would stick with good fuels.
With the Prius, it isn't meant for performance but then again, a cleaner and more powerful fuel makes for better combustion. I'd go for mid-range fuel on a prius it being a hybrid and all, but with anything else I would stick with good fuels.
KPARRIS-JONES, I think you are completely unaware of the relationship between temperature and MPG in the Prius, a lot of it is to do with how much the gasoline engine runs to produce heat for cabin warming.
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result !
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result !
Auto Express did a comparison between supermarket fuels and "brand" fuels. It wasn't that long ago, but I forget exactly what the results were beyond the supermarket fuels being as good as the "brand" fuels.
They didn't include the higher octane premium fuels in the test, but from my own experience I was getting 5mpg more using Tesco 99 than normal Tesco 95 octane. (in a Civic). Since then I only ever put Tesco 99 in both the Prius and the wifes Mazda 6.
Might try it again in the Prius and see if its any different.
They didn't include the higher octane premium fuels in the test, but from my own experience I was getting 5mpg more using Tesco 99 than normal Tesco 95 octane. (in a Civic). Since then I only ever put Tesco 99 in both the Prius and the wifes Mazda 6.
Might try it again in the Prius and see if its any different.
[quote name='Jonathan Mason' post='975407' date='Feb 21 2010, 07:40 AM']Auto Express did a comparison between supermarket fuels and "brand" fuels. It wasn't that long ago, but I forget exactly what the results were beyond the supermarket fuels being as good as the "brand" fuels.[/quote]
They'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.
They'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.
Filled up at Morrison's Hull a couple of years ago and once my car came back from the garage after having the fuel tank removed and drained, the fuel system flushed out and everything checked over, it ran quite well (I still don't know what the contaminant was 
) and I suppose the other supermarket stations were just unlucky that a silicon contamination cost them thousands of pounds 
) and I suppose the other supermarket stations were just unlucky that a silicon contamination cost them thousands of pounds
Thanks for replies. From your comments it would appear the dealer was correct when he said any low grade fuel would be OK in the Prius. I look forward to improved MPG as the OAT increases. Last August on a hot day I got 63 MPG.
[quote name='Seamaster73' post='975421' date='Feb 21 2010, 11:04 AM'][quote name='Jonathan Mason' post='975407' date='Feb 21 2010, 07:40 AM']Auto Express did a comparison between supermarket fuels and "brand" fuels. It wasn't that long ago, but I forget exactly what the results were beyond the supermarket fuels being as good as the "brand" fuels.[/quote]
They'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.
[/quote]
Never use anything except Shell V Power. Most experienced mechanics will tell you of the "Italian Tune up" for an ailing motor is a tankful of this and a blast up the motorway. Read Honest John's experience in the Daily Telegraph.
Pkram
They'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.
[/quote]
Never use anything except Shell V Power. Most experienced mechanics will tell you of the "Italian Tune up" for an ailing motor is a tankful of this and a blast up the motorway. Read Honest John's experience in the Daily Telegraph.
Pkram
Has anyone seen a Morrisons, Sainsbury or Tesco refinery ?
Where do some people think their fuel comes from when they buy it at a supermarket ?
Where do some people think their fuel comes from when they buy it at a supermarket ?
[quote name='KPARRIS-JONES' post='975394' date='Feb 21 2010, 02:54 AM']They aren't as refined and are always cheaper for a reason. [/quote]
All fuels are refined to the same standard....the only difference is the type and amount of additives added to the fuel has it is being loaded into the roadcar for delivery to the service stations.
Believe me when I say, you will not find inside a refinery, this tank for Asda grade fuel, that tank for Tesco grade fuel, it is complex enough blending the four main types of fuel you see on the forecourt, plus the dozens of other different refinery products.
[quote name='GIDDLEPIN' post='975425' date='Feb 21 2010, 10:19 AM'](I still don't know what the contaminant was )[/quote]
More than likely just (rain / ground) water in the bottom of the holding tank......and that can happen at any service station.
[quote name='martswain' post='975446' date='Feb 21 2010, 11:20 AM']Has anyone seen a Morrisons, Sainsbury or Tesco refinery ?
Where do some people think their fuel comes from when they buy it at a supermarket ?[/quote]
It is more than likely that the nearest refinery to your location, supplies most of the service stations in that area, what ever the name above the door of that particular service station. If for no other reason than to keep transportation costs down.
General rule: modern CR diesels with all their recirc valves and emissions filters are fussier drinkers than petrol engined cars and generally benefit from fuels with cleaner burning additives.
For petrol engined cars, some cars will run happier on the additives of a certain brand, whether it be supermarket or major. So look out for the brands your car is happy with and avoid those that it doesn't like.
Running super-unleaded in the Prius?
If your happy with it, stick with it. But for me the point of the Prius is to save money. I'll pay a little extra for fuel I know the car will perform well with but I think you have to balance any extra mpg against the additional cost of the super-unleaded. Personally, if the price differential was approaching 10p per litre over normal unleaded, I think the economics of using super-unleaded are looking shaky.
[/quote]All fuels are refined to the same standard....the only difference is the type and amount of additives added to the fuel has it is being loaded into the roadcar for delivery to the service stations.
Believe me when I say, you will not find inside a refinery, this tank for Asda grade fuel, that tank for Tesco grade fuel, it is complex enough blending the four main types of fuel you see on the forecourt, plus the dozens of other different refinery products.
[quote name='GIDDLEPIN' post='975425' date='Feb 21 2010, 10:19 AM'](I still don't know what the contaminant was
)[/quote]More than likely just (rain / ground) water in the bottom of the holding tank......and that can happen at any service station.
[quote name='martswain' post='975446' date='Feb 21 2010, 11:20 AM']Has anyone seen a Morrisons, Sainsbury or Tesco refinery ?
Where do some people think their fuel comes from when they buy it at a supermarket ?[/quote]
It is more than likely that the nearest refinery to your location, supplies most of the service stations in that area, what ever the name above the door of that particular service station. If for no other reason than to keep transportation costs down.
General rule: modern CR diesels with all their recirc valves and emissions filters are fussier drinkers than petrol engined cars and generally benefit from fuels with cleaner burning additives.
For petrol engined cars, some cars will run happier on the additives of a certain brand, whether it be supermarket or major. So look out for the brands your car is happy with and avoid those that it doesn't like.
Running super-unleaded in the Prius?
If your happy with it, stick with it. But for me the point of the Prius is to save money. I'll pay a little extra for fuel I know the car will perform well with but I think you have to balance any extra mpg against the additional cost of the super-unleaded. Personally, if the price differential was approaching 10p per litre over normal unleaded, I think the economics of using super-unleaded are looking shaky.
[quote name='martswain' post='975403' date='Feb 21 2010, 06:05 AM']KPARRIS-JONES, I think you are completely unaware of the relationship between temperature and MPG in the Prius, a lot of it is to do with how much the gasoline engine runs to produce heat for cabin warming.
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result ![/quote]
I applied my theory to cars in general. I don't have a prius so know I am not aware of how it operates and its ideal temperatures. Sorry if I haven't provided useful information.
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result ![/quote]
I applied my theory to cars in general. I don't have a prius so know I am not aware of how it operates and its ideal temperatures. Sorry if I haven't provided useful information.
K-PARRIS_JONES. All information is useful. Thank you for taking time to reply to my question. I appreciate your comments.
Regards Chris.
Regards Chris.
I had the same feeling to-day, having bought supermarket (Sainsbury unleaded 95) and getting a good couple of mpg lower (possibly worse) than I'd get with other premium unleaded.
I think I'll keep an eye out on results.
Of course, we've had biting winds over the past couple of days, but I'd say that I've been through other snow falls without this loss of mileage.
I think I'll keep an eye out on results.
Of course, we've had biting winds over the past couple of days, but I'd say that I've been through other snow falls without this loss of mileage.
Maybe these web pages will help...
[quote]In 2004 Sainsbury's struck a deal with BP and it is believed they now supply all of Sainsbury's fuel.[/quote][url="http://www.petrolprices.com/sainsburys.html"]http://www.petrolprices.com/sainsburys.html[/url]
[quote]Tesco supplies its forecourts with Super Unleaded 99 Octane, one of the highest-octane petrol available in the UK. The fuel is a blend of 5% bio-ethanol, and has been available since mid-November 2005, at selected filling stations across the UK. This Fuel is supplied to Tesco by Greenergy[/quote][url="http://www.petrolprices.com/tesco.html"]http://www.petrolprices.com/tesco.html[/url]
[quote]Morrisons supermarket petrol stations sell a range of fuels, once Shell and then Texaco but now they sell their own brand. They are a leading retailer of LPG Autogas, with 45 stations selling this more environmentally and economically friendly fuel.[/quote][url="http://www.petrolprices.com/morrisons.html"]http://www.petrolprices.com/morrisons.html[/url]
[quote]Asda once sold Texaco or Esso fuel but now provide own brand fuel. The Asda brand is popular for being one of the cheapest for fuel and is often in the news for starting the price war between supermarket fuel providers - by being the first to cut their prices.[/quote][url="http://www.petrolprices.com/asda.html"]http://www.petrolprices.com/asda.html[/url]
So previous experience of supermarket fuel could be different from the current supply as things have changed over the years.
[quote]In 2004 Sainsbury's struck a deal with BP and it is believed they now supply all of Sainsbury's fuel.[/quote][url="http://www.petrolprices.com/sainsburys.html"]http://www.petrolprices.com/sainsburys.html[/url]
[quote]Tesco supplies its forecourts with Super Unleaded 99 Octane, one of the highest-octane petrol available in the UK. The fuel is a blend of 5% bio-ethanol, and has been available since mid-November 2005, at selected filling stations across the UK. This Fuel is supplied to Tesco by Greenergy[/quote][url="http://www.petrolprices.com/tesco.html"]http://www.petrolprices.com/tesco.html[/url]
[quote]Morrisons supermarket petrol stations sell a range of fuels, once Shell and then Texaco but now they sell their own brand. They are a leading retailer of LPG Autogas, with 45 stations selling this more environmentally and economically friendly fuel.[/quote][url="http://www.petrolprices.com/morrisons.html"]http://www.petrolprices.com/morrisons.html[/url]
[quote]Asda once sold Texaco or Esso fuel but now provide own brand fuel. The Asda brand is popular for being one of the cheapest for fuel and is often in the news for starting the price war between supermarket fuel providers - by being the first to cut their prices.[/quote][url="http://www.petrolprices.com/asda.html"]http://www.petrolprices.com/asda.html[/url]
So previous experience of supermarket fuel could be different from the current supply as things have changed over the years.
[quote name='KPARRIS-JONES' post='975525' date='Feb 21 2010, 03:40 PM'][quote name='martswain' post='975403' date='Feb 21 2010, 06:05 AM']KPARRIS-JONES, I think you are completely unaware of the relationship between temperature and MPG in the Prius, a lot of it is to do with how much the gasoline engine runs to produce heat for cabin warming.
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result ![/quote]
I applied my theory to cars in general. I don't have a prius so know I am not aware of how it operates and its ideal temperatures. Sorry if I haven't provided useful information.
[/quote]
In general colder air decreases MPG as said above (but increases power)
Think about it, colder, air contains more oxygen than the same volume of warmer air due to the increased density as you correctly pointed out. What happens though is to keep the air fuel ratio right the ECU sends in more fuel accordingly hence MPG goes down.
As for lower octane fuel yeiling a poorer MPG, this is true in engines designed to run at higher octane (usually performance engines). Lower octane fuel causes knocking, when the ECU detects this is retards the ignition timing to elimitate it as a safety measure, at the expence of efficiancy.
There is never any more oxygen in lower temperature air, all that varies is air density, and your fuel injection system will adjust for this.
Chris, my last 4 petrol cars areas follows : Porsche 911, Prius Gen 2, Grand Cherokee SRT8 and currently a Prius Gen 3 T Spirit.
I have tried using BP Premium unleaded v Tesco Premium unleaded in the Porsche and SRT8 with no perceptible variation in economy, even though the Tesco version is actually higher octane.
Nobody in any service department mentioned anything about the state of spark plugs or queried the fuels I had used.
In my first Prius, I also tried comparing BP unleaded with using their Premium unleaded, again with no difference and eventually for convenience reasons went back to Tesco's ordinary stuff, no point in driving extra miles just to fill up !
Tesco unleaded gave the same results as BP.
Gen 3 is now running solely on Tesco unleaded.
Comparing the Gen 2 and 3, the 2 seemed more sensitive to temperature than the latest model.
As my journeys are regular I think my observations are pretty valid, you can put in any fuel you like and you will not notice any difference.
A cold morning however will produce a much more startling result ![/quote]
I applied my theory to cars in general. I don't have a prius so know I am not aware of how it operates and its ideal temperatures. Sorry if I haven't provided useful information.
[/quote]
In general colder air decreases MPG as said above (but increases power
)Think about it, colder, air contains more oxygen than the same volume of warmer air due to the increased density as you correctly pointed out. What happens though is to keep the air fuel ratio right the ECU sends in more fuel accordingly hence MPG goes down.
As for lower octane fuel yeiling a poorer MPG, this is true in engines designed to run at higher octane (usually performance engines). Lower octane fuel causes knocking, when the ECU detects this is retards the ignition timing to elimitate it as a safety measure, at the expence of efficiancy.
Personally I find Shell Unleaded is cheaper than Tesco and Sainsbury Unleaded. Strange.
On the consumption issue it may be appropriate to consider that after a cold spell the fuel you pump into your car will be denser and so will contain more energy than the same volume would in the summer.
On the difference between brands issue here is an anecdotal comment. Some years ago our local Morrisons always sold Texaco. They changed to Jet and there was a noticeable drop in my mpg. I moved to Shell and my mpg went up. My daughter had always thought that she got poorer mpg when she filled up at another Morrisons which she did quite often. After the change at our local branch she asked at the other one where she was told they had always used Jet. At the time we were both doing a lot of repetitive journeys and making regular fills - the difference was just over 5% for both of us.
On the difference between brands issue here is an anecdotal comment. Some years ago our local Morrisons always sold Texaco. They changed to Jet and there was a noticeable drop in my mpg. I moved to Shell and my mpg went up. My daughter had always thought that she got poorer mpg when she filled up at another Morrisons which she did quite often. After the change at our local branch she asked at the other one where she was told they had always used Jet. At the time we were both doing a lot of repetitive journeys and making regular fills - the difference was just over 5% for both of us.
Our local Esso station pricematches the Asda next door, so we're quite lucky.
The petrol station a few hundred yards further down the road is a couple of pence more expensive but located at the top of the M606, so people pay for the convenience factor.
Jet petrol used to be rubbish, imho, a few years ago.
I had a Fiat Panda back then that was running poorly. It turns out the carb was silted up with black bits.
The first thing the mechanic asked was whether I used Jet petrol as he had seen quite a few cars like that in the area.
Maybe that petrol station had dirty tanks?
These days fuel supposedly comes from the same refineries, but they must have different store tanks of different grades.
The previous silicon contaminated material the supermarkets used didn't get into the premium brands afaik, and was from a blender who might source offspec material from anywhere then blend to the very lowest edge of the sales spec.
I think the main brands would have more consistency of supply, and offspec material be blended and go to the lesser brands?
The petrol station a few hundred yards further down the road is a couple of pence more expensive but located at the top of the M606, so people pay for the convenience factor.
Jet petrol used to be rubbish, imho, a few years ago.
I had a Fiat Panda back then that was running poorly. It turns out the carb was silted up with black bits.
The first thing the mechanic asked was whether I used Jet petrol as he had seen quite a few cars like that in the area.
Maybe that petrol station had dirty tanks?
These days fuel supposedly comes from the same refineries, but they must have different store tanks of different grades.
The previous silicon contaminated material the supermarkets used didn't get into the premium brands afaik, and was from a blender who might source offspec material from anywhere then blend to the very lowest edge of the sales spec.
I think the main brands would have more consistency of supply, and offspec material be blended and go to the lesser brands?
[quote name='posing' post='976476' date='Feb 23 2010, 02:58 PM']Personally I find Shell Unleaded is cheaper than Tesco and Sainsbury Unleaded. Strange.[/quote]
We have a similar situation. Our Tesco is more expensive than Esso and Shell (although our Shell garage has just closed and is being turned into flats
).
We have a similar situation. Our Tesco is more expensive than Esso and Shell (although our Shell garage has just closed and is being turned into flats
).
[quote name='johalareewi' post='976847' date='Feb 24 2010, 09:31 AM'](although our Shell garage has just closed and is being turned into flats ).[/quote]
This is happening in a few places - petrol stations turn into flats! But no new ones built elsewhere........
).[/quote]This is happening in a few places - petrol stations turn into flats! But no new ones built elsewhere........
Think about it, colder, air contains more oxygen than the same volume of warmer air due to the increased density as you correctly pointed out. What happens though is to keep the air fuel ratio right the ECU sends in more fuel accordingly hence MPG goes down.
I [b]have [/b]been having a think on the journey from Pattaya to Bangkok, but this not going to turn into an argument or slagging match because I am not an automotive engineer.
Air gets colder, more fuel required to keep the ratio correct.
More fuel equals more power produced, therefore we accelerate.
If we allow this higher speed, then what happens to the MPG ?
If we back off to maintain the current speed, then what ?
Air resistance and rolling resistance are not linear either as far as I remember.
There are too many variables to actually know what will happen to the MPG when the air gets colder.
The only fact seems to be that the Prius, in normal mixed road driving, delivers considerably less MPG in COLD weather.
It needs to keep itself and it's occupants warm and the only way to do that is run the petrol engine more often.
So, here I sit in sunny Bangkok, wondering if I will get back to Glasgow tomorrow without any weather delays and if my T Spirit will burst into life after nearly 4 weeks sat idle.
I [b]have [/b]been having a think on the journey from Pattaya to Bangkok, but this not going to turn into an argument or slagging match because I am not an automotive engineer.
Air gets colder, more fuel required to keep the ratio correct.
More fuel equals more power produced, therefore we accelerate.
If we allow this higher speed, then what happens to the MPG ?
If we back off to maintain the current speed, then what ?
Air resistance and rolling resistance are not linear either as far as I remember.
There are too many variables to actually know what will happen to the MPG when the air gets colder.
The only fact seems to be that the Prius, in normal mixed road driving, delivers considerably less MPG in COLD weather.
It needs to keep itself and it's occupants warm and the only way to do that is run the petrol engine more often.
So, here I sit in sunny Bangkok, wondering if I will get back to Glasgow tomorrow without any weather delays and if my T Spirit will burst into life after nearly 4 weeks sat idle.
[quote name='martswain' post='976859' date='Feb 24 2010, 10:42 AM']Think about it, colder, air contains more oxygen than the same volume of warmer air due to the increased density as you correctly pointed out. What happens though is to keep the air fuel ratio right the ECU sends in more fuel accordingly hence MPG goes down.
I [b]have [/b]been having a think on the journey from Pattaya to Bangkok, but this not going to turn into an argument or slagging match because I am not an automotive engineer.
Air gets colder, more fuel required to keep the ratio correct.
More fuel equals more power produced, therefore we accelerate.
If we allow this higher speed, then what happens to the MPG ?
If we back off to maintain the current speed, then what ?
Air resistance and rolling resistance are not linear either as far as I remember.
There are too many variables to actually know what will happen to the MPG when the air gets colder.
The only fact seems to be that the Prius, in normal mixed road driving, delivers considerably less MPG in COLD weather.
It needs to keep itself and it's occupants warm and the only way to do that is run the petrol engine more often.
So, here I sit in sunny Bangkok, wondering if I will get back to Glasgow tomorrow without any weather delays and if my T Spirit will burst into life after nearly 4 weeks sat idle.[/quote]
WHS - I contemplated commenting earlier, but decided not to bother. The issue is a very complex one. The oxygen sensor operates to try to maintain an air/fuel ratio close to stoichiometric (i.e. just enough air to burn all the fuel) at light loads. It is not exactly stoichiometric because what happens in the cylinder happens too fast for complete mixing, so they allow a bit spare. Stoichiometric combustion leads to very high temperatures and so at high speeds and loads, the mixture is made richer to keep down the temperature and avoid damage. Additionally, modern vehicles can mix cold air direct from the environment with air that has been heated by passing it over some hot part of the engine/exhaust system. A thermostat operates a mixing system to keep the temperature of the induced air more-or-less constant.
I am sure that martswain is right and that the major reasons for poorer consumption in the winter are associated with needing to use more energy to keep things warm and to deal with the greater pumping losses resulting from the higher viscosity of cold lubricating fluids etc. The energy loss on short journeys increases dramatically because of the greater thermal inertia that has to be overcome every time the vehicle is started.
I [b]have [/b]been having a think on the journey from Pattaya to Bangkok, but this not going to turn into an argument or slagging match because I am not an automotive engineer.
Air gets colder, more fuel required to keep the ratio correct.
More fuel equals more power produced, therefore we accelerate.
If we allow this higher speed, then what happens to the MPG ?
If we back off to maintain the current speed, then what ?
Air resistance and rolling resistance are not linear either as far as I remember.
There are too many variables to actually know what will happen to the MPG when the air gets colder.
The only fact seems to be that the Prius, in normal mixed road driving, delivers considerably less MPG in COLD weather.
It needs to keep itself and it's occupants warm and the only way to do that is run the petrol engine more often.
So, here I sit in sunny Bangkok, wondering if I will get back to Glasgow tomorrow without any weather delays and if my T Spirit will burst into life after nearly 4 weeks sat idle.[/quote]
WHS - I contemplated commenting earlier, but decided not to bother. The issue is a very complex one. The oxygen sensor operates to try to maintain an air/fuel ratio close to stoichiometric (i.e. just enough air to burn all the fuel) at light loads. It is not exactly stoichiometric because what happens in the cylinder happens too fast for complete mixing, so they allow a bit spare. Stoichiometric combustion leads to very high temperatures and so at high speeds and loads, the mixture is made richer to keep down the temperature and avoid damage. Additionally, modern vehicles can mix cold air direct from the environment with air that has been heated by passing it over some hot part of the engine/exhaust system. A thermostat operates a mixing system to keep the temperature of the induced air more-or-less constant.
I am sure that martswain is right and that the major reasons for poorer consumption in the winter are associated with needing to use more energy to keep things warm and to deal with the greater pumping losses resulting from the higher viscosity of cold lubricating fluids etc. The energy loss on short journeys increases dramatically because of the greater thermal inertia that has to be overcome every time the vehicle is started.
martswain is now very tired so I will not comment any further on the Prius consumption, thanks Sagitar for the detailed explanation !
It's 0140 in Bangkok and 40 minutes until I spend 12 hours in a large aluminium tube at 30-38 thousand feet with an OAT somewhere in the -50's.
I am SO looking forward to being freezing cold at home in Troon tomorrow...
It's 0140 in Bangkok and 40 minutes until I spend 12 hours in a large aluminium tube at 30-38 thousand feet with an OAT somewhere in the -50's.
I am SO looking forward to being freezing cold at home in Troon tomorrow...
[quote name='Chris Dance' timestamp='1266691368' post='975237']
Recently I filled up with cheaper fuel from Asda. At the present time it is giving me the lowest MPG I have ever had 45.5 on my Gen 2 T spirit. Maybe it is the colder weather only +3 today. Does any other Prius owner experience lower MPG with cheaper super market fuels?
With my Avensis I was told by the dealer it is OK to use the cheap fuels but every so often put the very best fuel you can in the tank. When I purchased the Prius dealer said just use any low octane fuel. ???
[/quote]
Yes. I have filled up three times over last 2 weeks with fuel from ASDA and I think that my fuel economy has suffered . I seem to be getting around 50 mpg instead of the 59 - 60 mpg that I normally see in my Gen3 Prius when buying from Shell. Then again I have also assumed that it is due to the return of the colder weather.
Does anybody really know if there is a significant difference between Supermarket fuel & Shell normal unleaded fuelsave?
Recently I filled up with cheaper fuel from Asda. At the present time it is giving me the lowest MPG I have ever had 45.5 on my Gen 2 T spirit. Maybe it is the colder weather only +3 today. Does any other Prius owner experience lower MPG with cheaper super market fuels?
With my Avensis I was told by the dealer it is OK to use the cheap fuels but every so often put the very best fuel you can in the tank. When I purchased the Prius dealer said just use any low octane fuel. ???
[/quote]
Yes. I have filled up three times over last 2 weeks with fuel from ASDA and I think that my fuel economy has suffered . I seem to be getting around 50 mpg instead of the 59 - 60 mpg that I normally see in my Gen3 Prius when buying from Shell. Then again I have also assumed that it is due to the return of the colder weather.
Does anybody really know if there is a significant difference between Supermarket fuel & Shell normal unleaded fuelsave?
Read all the above with interest... Only one person hit the nail somewhere near the head....
Morrisons, Tesco, Sainsbury, all collect their fuel in Essex from West Thurrock Vopak terminal/coryton refinery.
I can only assume the pipeline to the shell terminal next door contains better fuel than goes into the above mentioned tankers,
It all comes from the same ships, which come from the same terminals abroad which comes out of the same ground....
frankly, like most people, I will go to the nearest filling station, which in my case luckily is Tesco, i can see no point in using half a gallon to get to 'the cheapest' petrol station, or a BP station 'cos it's better'
Petrol makes the engine work, the right foot gives you economy, the government wins whichever brand you use!
Morrisons, Tesco, Sainsbury, all collect their fuel in Essex from West Thurrock Vopak terminal/coryton refinery.
I can only assume the pipeline to the shell terminal next door contains better fuel than goes into the above mentioned tankers,
It all comes from the same ships, which come from the same terminals abroad which comes out of the same ground....
frankly, like most people, I will go to the nearest filling station, which in my case luckily is Tesco, i can see no point in using half a gallon to get to 'the cheapest' petrol station, or a BP station 'cos it's better'
Petrol makes the engine work, the right foot gives you economy, the government wins whichever brand you use!
[quote name='Chris Dance' timestamp='1266691368' post='975237']
Recently I filled up with cheaper fuel from Asda. At the present time it is giving me the lowest MPG I have ever had 45.5 on my Gen 2 T spirit. Maybe it is the colder weather only +3 today. Does any other Prius owner experience lower MPG with cheaper super market fuels?
With my Avensis I was told by the dealer it is OK to use the cheap fuels but every so often put the very best fuel you can in the tank. When I purchased the Prius dealer said just use any low octane fuel. ???
[/quote]
Recently I filled up with cheaper fuel from Asda. At the present time it is giving me the lowest MPG I have ever had 45.5 on my Gen 2 T spirit. Maybe it is the colder weather only +3 today. Does any other Prius owner experience lower MPG with cheaper super market fuels?
With my Avensis I was told by the dealer it is OK to use the cheap fuels but every so often put the very best fuel you can in the tank. When I purchased the Prius dealer said just use any low octane fuel. ???
[/quote]
waitrose fuel gave me 4mpg extra when i had my avensis 1.6 i returned to tesco fuel several times and this confirmed waitrose is much much better and the SAME price per litre in my area aswell. Pumped marked up at waitrose as PREMIUM unleaded i class premium better qaulity than unleaded or regular unleaded i may be wrong but my aygo is running on waitrose fuel and getting 63.6mpg country lanes/dual/town driving 410miles per week. Wont bother trying out any other fuel stations as im happy with this figure. Waitrose swaffham norfolk £127.9 per litre super is only 3p yes 3p dearer so may try this out
Can't add much except that my old Saab was smoother and more responsive when running on Shell V Power instead of normal branded 95.
If you are planning going on the continent with your Prius this summer I would recommend that you avoid filling with SP95-E10 (10% ethanol) fuel which is now replacing normal 95 octane on some forecourts in France. I used one tank and the car was very sluggish, struggled to get up hills on the motorway and the consumption increased. When I stopped and filled up with normal 95octane the car went romping up the next hill with no problem and the mpg figure increased by about 5mpg.
If you are planning going on the continent with your Prius this summer I would recommend that you avoid filling with SP95-E10 (10% ethanol) fuel which is now replacing normal 95 octane on some forecourts in France. I used one tank and the car was very sluggish, struggled to get up hills on the motorway and the consumption increased. When I stopped and filled up with normal 95octane the car went romping up the next hill with no problem and the mpg figure increased by about 5mpg.
Using 99 octane fuel in a Prius will give lower MPG, this fuel has a lower callorific value than 95 octane and will produce less power in an engine that is not designed to run on it.
In theory but then again the Yanks use 91 octane (87 on US scale) and they object to using 95 octane (our normal unleaded) as they say it gives less mpg's. Weird as we seem to get the same mpg's as they do (even accounting for their smaller gallon at 3.7 litres compared to 4.5 litres for ours).
Perhaps the car adjusts for the different fuel using knock sensors etc?
Perhaps the car adjusts for the different fuel using knock sensors etc?
Cod air does tend to cause an increase in fuel use in petrol engines due to the whole colder air = higher air density thing, but if that was the only reason then my diesel lump wouldn't be affected at all (The accelerator in a diesel controls fuel flow rather than air flow throttling as in a petrol engine).
The main reason for the mpg loss is because the engine block takes much longer to warm up to its most efficient operating temp range in cold weather, and as soon as you get stuck in slow traffic and idle it cools down again. My Yaris really hates the cold as it generates sod-all heat unless I thrash the nuts off of it, so in the winter I'm usually freezing my nuts off!!
The Prius is particularly vulnerable to this because its petrol engine is (Under normal circumstances) never run long enough to remain at optimal operating temperature for a decent amount of time.
But this is why you see taxi drivers sticking a whopping great hunk of cardboard over their radiator grills in winter, so the car heats up faster and stays heated up so the engine runs more efficiently.
As for fuel, I have found V-Power Diesel particularly crap in cold weather unless you're hitting motorway speeds. I went back to normal diesel last week (Sainsburys 'City diesel') and am getting better mpgs for urban driving than I was getting with V-Power.
V-Power really doesn't work for me unless I'm doing 1800rpm or more (Then it's great) but when driving off-turbo (Which is what you want for maximum efficiency!) normal diesel seems to be deliver noticeably more torque which lets me abuse the high gears without labouring the engine . I still haven't tried Shell's Fuelsave Diesel yet tho', mainly because it's 5p more than my supermarket fuel 
The main reason for the mpg loss is because the engine block takes much longer to warm up to its most efficient operating temp range in cold weather, and as soon as you get stuck in slow traffic and idle it cools down again. My Yaris really hates the cold as it generates sod-all heat unless I thrash the nuts off of it, so in the winter I'm usually freezing my nuts off!!
The Prius is particularly vulnerable to this because its petrol engine is (Under normal circumstances) never run long enough to remain at optimal operating temperature for a decent amount of time.
But this is why you see taxi drivers sticking a whopping great hunk of cardboard over their radiator grills in winter, so the car heats up faster and stays heated up so the engine runs more efficiently.
As for fuel, I have found V-Power Diesel particularly crap in cold weather unless you're hitting motorway speeds. I went back to normal diesel last week (Sainsburys 'City diesel'
) and am getting better mpgs for urban driving than I was getting with V-Power.V-Power really doesn't work for me unless I'm doing 1800rpm or more (Then it's great
) but when driving off-turbo (Which is what you want for maximum efficiency!) normal diesel seems to be deliver noticeably more torque which lets me abuse the high gears without labouring the engine . I still haven't tried Shell's Fuelsave Diesel yet tho', mainly because it's 5p more than my supermarket fuel
The water is muddied a bit in the USA because of the use of alcohol in the fuel and yes the prius does adjust ignition timing via knock sensors if you use a fuel that is below spec, but if you go above spec no knock from the engine and it runs at the timing pre set by Toyota and will not advance the ignition to try to take advantage of higher octane feul.
But a lot of our fuel has various amounts of ethanol in it and I think that's where some of the differences occur between 'normal' and some supermarket blends. I'm sure I've read somewhere that there are different British Standards for the differing petrols with differing ethanol amounts in it. Does anyone with knowledge know if this is true?
A few petrol stations carry E/blends but they have to be clearly marked as it can damage some engines. The EU has decided that by 2013 all fuel must contain 5to10% ethanol i pity people with metal fuel tanks as ethanol is corrosive.
I've just had a look at my fuel consumption for the last few months, compared with the same few months a year ago. It has improved by 2-3 mpg. This included December, which was colder than the previous year, so I would have expected consumption to be worse, not better.
As far as I can see, there are three possible reasons:
[list]
[*]The car is now very well run in. 30-40,000 miles against 0-10,000.
[*]I started using my own oil (Motul 0w-20 from Opie) instead of Toyota 0W-20.
[*]I've been using Shell Fuelsave petrol since it was introduced.
[/list]
Timings suggest the oil. I don't think it's the garage using 5W-30, and charging for 0W-20. The mpg change isn't big enough for that.
I don't think it's the running in. I didn't have the same improvement with the old Gen II, with very similar mileages involved.
The improvements kicked in about 2 months later Shell introduced Fuelsave. So either it's not that, or it takes a couple of months (4-5,000 miles) for it to really kick in.
However, my son who is now driving my old Gen II (85,000 miles) has noticed a distinct improvement in mpg after changing from Tesco to Shell (new jobe, no longer near a Tesco filling station), with the engine apparently running more smoothly. He thinks more than enough to justify the loss of Tesco points.
FWIW. As far as I know there is no difference between brands in the underlying petrol. There can be a big difference in the additive package. I know that Shell does a lot of research to develop these, which is why I use it most of the time. The other oil majors are probably similar, while the supermarkets and others rely on whoever supplies their fuel - and even if they buy from a major, they may not get the same additive package.
[URL=http://www.fuelly.com/driver/AncientNerd/prius][IMG]http://www.fuelly.com/sig-uk/35661.png[/IMG][/URL]
As far as I can see, there are three possible reasons:
[list]
[*]The car is now very well run in. 30-40,000 miles against 0-10,000.
[*]I started using my own oil (Motul 0w-20 from Opie) instead of Toyota 0W-20.
[*]I've been using Shell Fuelsave petrol since it was introduced.
[/list]
Timings suggest the oil. I don't think it's the garage using 5W-30, and charging for 0W-20. The mpg change isn't big enough for that.
I don't think it's the running in. I didn't have the same improvement with the old Gen II, with very similar mileages involved.
The improvements kicked in about 2 months later Shell introduced Fuelsave. So either it's not that, or it takes a couple of months (4-5,000 miles) for it to really kick in.
However, my son who is now driving my old Gen II (85,000 miles) has noticed a distinct improvement in mpg after changing from Tesco to Shell (new jobe, no longer near a Tesco filling station), with the engine apparently running more smoothly. He thinks more than enough to justify the loss of Tesco points.
FWIW. As far as I know there is no difference between brands in the underlying petrol. There can be a big difference in the additive package. I know that Shell does a lot of research to develop these, which is why I use it most of the time. The other oil majors are probably similar, while the supermarkets and others rely on whoever supplies their fuel - and even if they buy from a major, they may not get the same additive package.
[URL=http://www.fuelly.com/driver/AncientNerd/prius][IMG]http://www.fuelly.com/sig-uk/35661.png[/IMG][/URL]
It's the oil!
If the garage used 5w30 then it hammers your mpgs (gen3 Prius only).
Don't believe me, check out some of my earlier posts from about a year ago. When they used 5w30 by mistake I couldn't get past 55 mpg unless I really really tried hard. When I use the correct 0w20 I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
If the garage used 5w30 then it hammers your mpgs (gen3 Prius only).
Don't believe me, check out some of my earlier posts from about a year ago. When they used 5w30 by mistake I couldn't get past 55 mpg unless I really really tried hard. When I use the correct 0w20 I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
[quote name='Grumpy Cabbie' timestamp='1298292794' post='1092728']
... I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
[/quote]
Those motorway roadworks are great for giving an mpg boost
... I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
[/quote]
Those motorway roadworks are great for giving an mpg boost
[quote name='Grumpy Cabbie' timestamp='1298292794' post='1092728']
It's the oil!
If the garage used 5w30 then it hammers your mpgs (gen3 Prius only).
Don't believe me, check out some of my earlier posts from about a year ago. When they used 5w30 by mistake I couldn't get past 55 mpg unless I really really tried hard. When I use the correct 0w20 I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
[/quote]
I believe you alright. The problem is that the comparison is with the first 10,000 miles, when the car was using the original factory fill oil, so it's unlikely to be a rogue factory fill of 5W-30. And it was filled by Toyota Japan, so no opportunity for Toyota GB to mess up! Also, I'd have expected a bigger improvement if it was the oil.
I would have said it was because the car has now been thoroughly run-in. However, there was no similar jump with the Gen II. Or is it that the GenIII runs in better than the Gen II?
It's the oil!
If the garage used 5w30 then it hammers your mpgs (gen3 Prius only).
Don't believe me, check out some of my earlier posts from about a year ago. When they used 5w30 by mistake I couldn't get past 55 mpg unless I really really tried hard. When I use the correct 0w20 I can get 75 or 80 mpg for long periods such as in a 50 mph motorway works zone.
[/quote]
I believe you alright. The problem is that the comparison is with the first 10,000 miles, when the car was using the original factory fill oil, so it's unlikely to be a rogue factory fill of 5W-30. And it was filled by Toyota Japan, so no opportunity for Toyota GB to mess up! Also, I'd have expected a bigger improvement if it was the oil.
I would have said it was because the car has now been thoroughly run-in. However, there was no similar jump with the Gen II. Or is it that the GenIII runs in better than the Gen II?
The engine in the gen3 has higher tolerances and needs the thinner oil. See other posts- Toyota UK even sent a mail round all dealers saying they MUST now use 0w20 as previously they said they could use 5w30 in certain circumstances for a temporary period.
If you doubt its got 0w20 in it then get the dealers to change it - maybe say you'll get in analised. Mine changed it half way through as I told them about the running issues (shown below) and though the oil was over filled. They changed it back to 0w20 and the problems stopped immediately.
The way I knew it wasn't 0w20 was that the car was much much quieter at cold start (5w30 is thicker), it was hesitant when the engine fired up (even when warm) and there was no power in Power mode. Also the mpg's were about 50-55 mpg at best. Went back to being a fabulous, smooth and very economical car once the correct oil was back in.
Let us all know how you get on.
If you doubt its got 0w20 in it then get the dealers to change it - maybe say you'll get in analised. Mine changed it half way through as I told them about the running issues (shown below) and though the oil was over filled. They changed it back to 0w20 and the problems stopped immediately.
The way I knew it wasn't 0w20 was that the car was much much quieter at cold start (5w30 is thicker), it was hesitant when the engine fired up (even when warm) and there was no power in Power mode. Also the mpg's were about 50-55 mpg at best. Went back to being a fabulous, smooth and very economical car once the correct oil was back in.
Let us all know how you get on.
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