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MG MGF Technical - Supermarket Petrol

Not one of the MGs but the Toyota failed to start yesterday morning. Weather was the unique British combination of just short of freezing and everything soaked in dampness. Cranked over normally, fired once, then cranked with a really strange noise but wouldn't fire again. Spark OK, fuel OK, cambelt OK, compression way down on one cylinder which was odd as it had been running fine. Battery cranking voltage was 8 point something which is lower than it should be but jumping it from the V8 (which started as normal) made no difference. As I had been cranking it a bit I put it on charge while I pondered things. Then tried again about half an hour later and it cranked faster and was obviously trying to fire. After about 30 secs of that it eventually staggered into life, obviously firing on 3 cylinders and sounding like one of the exhaust valves was sticking open. After a few moments of that it started running normally, presumably as the sticking valve unstuck. Between us my son and I have had this car over 10 years with nothing like it before, the only other difference being I had changed from using Shell ordinary unleaded to Tesco petrol just two tankfuls ago. I've heard other comments about supermarket petrol in the past, has anyone experienced anything like this?
Paul Hunt 2

Yes, with a Nissan twice. Same conditions you have outlined but low compression on all cylinders, the fuel change was to Esso.

I considered hydraulic tappets and dirty oil to be a possible cause.

Does oil turn to glue in the presence of some fuel additives????? Answers on a postcard.
Ken Waring

Tesco petrol will come from the same refinery that supplies all other petrol stations in your area.

Sam
Sam Murray

All of my cars for the last few years have had an exclusive diet of whatever is cheapest in the area. I've not yet been able to tell any difference running on Tesco's petrol or Shell's finest!
James King

Paul

I work at the large refinery here in Pembroke and can confirm as indicated by Sam that exactly the same fuel is used by the supermarkets as that by the leading brands.

To make separate fuel mixes just wouldn't make sense or be practicable - the different companies tankers come in and fill up from exactly the same tanks!

If there is a problem with the fuel, it is most likely to be as a result of water seeping into the forecourts own tanks but this is almost unknown.
Pete

Pete

Tescos now have their own fuel supply for 99

http://www.greenergy.com/products/99_octane.html

Optimax may also be a different fuel mix

The rest may use same fuel mix with different additives

Honest John FAQ
Feedback is that BP Ultimate diesel is the best diesel giving smoother running, more power and better economy to justify its higher price. Greenergy City Diesel sold by some supermarkets has the necessary lubricity. Shell Optimax is the best petrol giving better performance and economy for most (though not all) cars. Shell and Texaco petrol traditionally had the best detergent packages, but BP Ultimate petrol now has a good one too, and Esso has also introduced a high detergent petrol. Lack of detergent and a high proportion of short runs from cold is what causes most petrol engine fuel system problems, so if you buy your petrol from a supermarket seek written assurance that it at least meets and preferably far exceeds the British Standard for detergent in petrol

Not sure about last comment from HJ.

Paul

Paul

This thread was discussed between 09/01/2006 and 10/01/2006

MG MGF Technical index

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