Supermarket fuel - does it really give lower mpg ?

Strider590

thescouselander wrote: »

I dont think there is any difference. I have a sainsbury's petrol station at one end of the road and an Esso at the other. I fill the car at whatever petrol station I'm passing when the car needs refilling so I use supermarket fuel about half of the time. I do monitor fuel use every tank as increased usage could be a sign that something is wrong with the car but I've never noticed any difference between the Sainsburys and Esso petrol - it all seems the same as far as I can tell.

Are you relying on the highly inaccurate MPG displays on the dashboard or actually measuring/calculating it yourself?

sandiep

Petrol/Diesel is sold by the refineries in grades, the grade being the clarity of the fuel, and the grades do vary in price. Supermarkets do tend to buy a lower grade fuel than those such as Shell etc, particularly when they're in the middle of a petrol price war.

thescouselander

Strider590 wrote: »

Are you relying on the highly inaccurate MPG displays on the dashboard or actually measuring/calculating it yourself?

I usually calculate it myself using the amount of petrol shown on the reciept but I dont think it makes too much difference. If the trip computer is out of calibration the same error will be applied between one tank and the next so you can still make a good comparison between tanks using the computer.

As it happens the difference beween the computer and manual calculation is only about 1 mpg on my car.

david39

"Petrol/Diesel is sold by the refineries in grades, the grade being the clarity of the fuel, and the grades do vary in price. Supermarkets do tend to buy a lower grade fuel than those such as Shell etc, particularly when they're in the middle of a petrol price war"

Where do you get that information from, sandiep?

As Hammyman said, the tankers from all companies - Major brands, minor brands, supermarkets - all go under the same loading bays and draw the same basic products that meet the relevant European Standards. The refineries / storage depots do not hold different tanks of different grades of the same fuel. The only difference is in the additive-package which is stipulated by the buyer and added from a separate tank at the loading bay. These additives cost approximately 0.9 pence per litre.

There is no such thing as a price-war - it's a publicity stunt thought up years ago by advertising agencies to make the public think that the producers had the consumers' best interests at heart - and later carried on by the tabloids as a great headline banner. It goes along with them publicising that petrol is £6 per gallon when most motorists have never bought petrol by the gallon.

The cost of discounting the 5p off is carried as an overhead by the supermarket group out of it's advertising budget and paid for from the profits of their mainline business.

king100

Right the answer

Supermarkets use bog standard petrol and diesel.

Shell bog standard diesel has double dose additives so will be better same with the petrol.

Hence shell will be better and also do more mpg for you.

david39

I endorse what king100 says

thescouselander

king100 wrote: »

Right the answer

Supermarkets use bog standard petrol and diesel.

Shell bog standard diesel has double dose additives so will be better same with the petrol.

Hence shell will be better and also do more mpg for you.

I dont know if that is true but if it is I'm not sure the effect would be instantanious. Surely additives can only clean up your fuel system so that it runs more efficiently - this will probably require the use of the better petrol for several tanks before any effect is seen.

If your car is in good shape and running efficiently to begin with I dont think you woud see and difference other than the better petrol may prevent degradation of the fuel system.

At the end of the day 1 litre of supermarket fuel will have the same energy content as 1 litre of branded petrol so how can an increase in MPG be achieved?

david39

Additives in petrol will improve the efficiency of the engine by, amongst other things, reducing pre-ignition (also known as pinking) and improving the octane rating.

Strider590

thescouselander wrote: »

I dont know if that is true but if it is I'm not sure the effect would be instantanious. Surely additives can only clean up your fuel system so that it runs more efficiently - this will probably require the use of the better petrol for several tanks before any effect is seen.

If your car is in good shape and running efficiently to begin with I dont think you woud see and difference other than the better petrol may prevent degradation of the fuel system.

At the end of the day 1 litre of supermarket fuel will have the same energy content as 1 litre of branded petrol so how can an increase in MPG be achieved?

What people don't seem to grasp is that additives were primarily used to substitute qualities removed when we went over to unleaded petrol. This includes to name but a few, octane boosting, valve wear reduction, fuel system cleaning and lubrication.

The additives are added at the individual fuel station and therein lies the different between brand fuel and supermarket fuel. Additive quality.....
You can't measure quality and most people therefore choose to ignore it.

It's like buying a PC from <insert name of big cheap PC retailer> and expecting it to last as long as a custom PC built from top quality parts.

thescouselander

david39 wrote: »

Additives in petrol will improve the efficiency of the engine by, amongst other things, reducing pre-ignition (also known as pinking) and improving the octane rating.

Yes but if you buy 95 ron petrol at the supermarket its the same as the 95 ron you might buy at shell or similar so clearly, with regards to octane, the two sorts of petrol are equivalent.

Strider590 wrote: »

What people don't seem to grasp is that additives were primarily used to substitute qualities removed when we went over to unleaded petrol. This includes to name but a few, octane boosting, valve wear reduction, fuel system cleaning and lubrication.

The additives are added at the individual fuel station and therein lies the different between brand fuel and supermarket fuel. Additive quality.....
You can't measure quality and most people therefore choose to ignore it.

It's like buying a PC from <insert name of big cheap PC retailer> and expecting it to last as long as a custom PC built from top quality parts.

I think you are misusing the term "quality" here. Quality in a manufaturing sense is related to the repeatability of the manufacturing process and the tolerances to which the product is manufactured. It is doubtful that including additives to the base product from the refinary can fundimentally improve the quality of the petrol as such - although perhaps specification may be improved by adding benifits such as detergent effects or octane boosters etc.