Super Market Fuel

[Chris Dance]

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. ???

[KPARRIS-JONES]

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. :)

[martswain]

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 !

[Jonathan Mason]

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.

[Seamaster73]

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'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.

[GIDDLEPIN]

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

[Chris Dance]

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.

[Pkram]

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'd better be, otherwise the BSI (British Standard) designation that must be achieved by them is meaningless.

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

[martswain]

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 ?

[Fujisan]

They aren't as refined and are always cheaper for a reason. ;)

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.

(I still don't know what the contaminant was )

More than likely just (rain / ground) water in the bottom of the holding tank......and that can happen at any service station.

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 ?

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.

[KPARRIS-JONES]

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 !

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. ;)

[Chris Dance]

K-PARRIS_JONES. All information is useful. Thank you for taking time to reply to my question. I appreciate your comments.

Regards Chris.

[Colin321]

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.

[hertsnminds]

Maybe these web pages will help...

In 2004 Sainsbury's struck a deal with BP and it is believed they now supply all of Sainsbury's fuel.

http://www.petrolprices.com/sainsburys.html

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

http://www.petrolprices.com/tesco.html

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.

http://www.petrolprices.com/morrisons.html

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.

http://www.petrolprices.com/asda.html

So previous experience of supermarket fuel could be different from the current supply as things have changed over the years.

[Karma Supra]

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 !

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. ;)

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.

[posing]

Personally I find Shell Unleaded is cheaper than Tesco and Sainsbury Unleaded. Strange.

[Big Mike]

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.

[cootuk]

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?

[johalareewi]

Personally I find Shell Unleaded is cheaper than Tesco and Sainsbury Unleaded. Strange.

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 :( ).

[posing]

(although our Shell garage has just closed and is being turned into flats :( ).

This is happening in a few places - petrol stations turn into flats! But no new ones built elsewhere........

[martswain]

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 have 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.

[Sagitar]

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 have 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.

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]

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...

[retiree]

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. ???

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?

[Jan&tone]

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!