which fuel (petrol) - tunacat
I'm sure this topic appears in other threads, but was brought to mind when reading the recent 'which diesel fuel' thread.

This is a tale starting 10 years ago, so things may well be different/better now, but it?s absolutely true and with no exaggeration:
I had an Uno Turbo which over time developed a misfire. It was just about tolerable (to me, but maybe not to many people), but still not cured, when fitted with the expensive 3-prong sparkplugs this model was supposed to have. My next car was a Citroen AX, and curiously, that developed a pretty identical misfire. If you changed the plugs, it'd be ok for a week or so and then the problem would creep back. I ended up having it tested on a rolling-road setup. The testers did reproduce the misfire, but said they could find nothing actually faulty with the car; but had noticed a bit of a green glaze on the plugs, and they asked me if I used supermarket petrol, as they'd seen another car with similar-looking plugs, and that one had used s'mkt petrol. As it happened, with my job/residence/routine during the entire period of owning both the Uno and the AX, I filled up every week, regular as clockwork, at the supermarket's filling station immediately after doing my shopping (their petrol was cheaper, plus you got extra points on the s'mkt loyalty card). In fact, I realised that unless circumstances dictated that I had to fill up away from my home town, these two different cars had both been run exclusively on that s'market's petrol! I put new plugs in again, and then for some months only filled up at 'name brand? petrol stations - and the misfire never recurred.

I'm sure it's fine to use from time to time, but since then I would no longer use supermarket fuel ALL the time. In any case, the price advantage seems much lower nowadays than it used to be.
which fuel (petrol) - StuW
This topic has been gone over many times before but and many have claimed that their cars have peformed worst with supermarket petrol less mpg less power etc. But i really cannot understand why there are only around (i think) 7 oil refineries in the country so all the petrol can only come from a limited number of areas. Higher octane fuel like Shell Optimax will probably made separately but as for normal unleaded i don't see how it can be any different from a supermarket to shell. I imagine that all petrol has like most things has to meet a specific standard and i can't believe an oil refinery would deliberately make a poor quality petrol specifically for supermarkets. After oil the tankers all go to the same place to collect it and bring it to the petrol station.
I can't explain why two of your cars would develop the misfire you describe but i fill up with supermarket petrol all the time and my car is still running perfect despite age and high miles.
which fuel (petrol) - steveb
You are largely correct, most petrol comes from the same source at the refinery, it is however the additives that go into each tanker coming out of the gates that makes the difference, both in quality and cost.

Branded fuel is more likely to have the higher quality additives - Shell/Esso etc, rather than the supermarket variety which will only have the minimum to keep the cost down.

which fuel (petrol) - tunacat
That tallies with what the chaps at the rolling-road test station said at the time - yes, it all starts out as the same petrol, probably meeting the minimum standards YSD refers-to, but then it has different proportions of additives added, depending on which brand of filling station it ends up in.

Maybe the supermarket I used didn't have any additives put in at all!

Anyone any experience of driving a tanker and delivering the stuff to the filling stations? Do they (always) put the additives in before they fill up the road tanker, or do they do it AT the filling station once they've refilled the underground tanks?
which fuel (petrol) - mark999
The major petrol companies add a keep clean dose of additive to the fuel. Some Supermarkets claim to also.
From my short time in the additives industry certainly saw the benefit of using enough additive. Namely clean injectors and inlet valves. (you do however get ~10% more cylinder head deposits.)

I don't know if practices have changed but I seem to remember that the tanker drivers carried a bottle of additive that thet dosed in at the fuel station.

The additives industry is a vert cut throat business and often fuel companies would choose price rather than quality.
which fuel (petrol) - johnny l.
I owned a Fiat Uno 1.1 Fire and would fill it up from the local supermarket. The result was consistent mis-firing when you put your foot down from a standstill. Worrying if you are pulling out into fast moving traffic. I changed to non-supermarket petrol and the problem went away. I didn't believe it was the fuel at first so I ran the tank down and tried the supermarket fuel again, and the problem came back. I didn't go to supermarkets again with the Uno.
I now own a Citroen ZX diesel, and even supermarket diesel diesn't seem to burn as well. Not as badly as the petrol, but still noticeable.
I have talked to a friend with a VW Golf Mk 5 1.4, and he doesn't touch supermarket fuel after he experienced similar problems to my own.

In conclusion, I am not imagining this. I would like to save money as much as anyone else, but I would advise everyone to steer clear of supermarket fuels.

which fuel (petrol) - enigma2
I drive a diesel which averages 75mpg. However, I too used Asda's diesel fuel and Jet's. The consumption dropped to 68mpg. I then decided to fill up at a Shell garage and the mpg increased. Must of been the quality of the fuel.
which fuel (petrol) - J Bonington Jagworth
"steer clear of supermarket fuels"

Or add Redex, perhaps...
which fuel (petrol) - Andrew-T
JBJ - for the price of the Redex you may as well fill up at the Shell place instead.
which fuel (petrol) - Vin {P}
I note that, despite repeated airings in this forum, no-one ever seems to have anything but anecdotal evidence. Has no car magazine or consumer organisation ever done a test on this?

My anecdotal evidence? I run an Omega (see thread on running costs in Technical) and I get 31mpg (almost exactly). For 4,000 miles I ran it on Optimax only and got 31.0, 29.4, 32.7, 30.6 for each respective 1000 miles. The rest of the time, it's on supermarket (Tesco) fuels 95% of the time. Hardly a scientific test, I know, but more evidence.

Doubtless I'll be told I'm killing the engine. Well, it's at 80K miles with no (touch wood) apparent problems.

If anyone can come up with empirical evidence to show I'm wrong, I'll change tomorrow. Until then, it's Tesco for me. (By the way, not because it's particularly cheaper but because it's on my way out of Southampton and I get money off my shopping)

which fuel (petrol) - jud
95% of the petrol i use is asda petrol, using it with one Toyota and two primera's plus the present A4, i have never had any running problems of any sort. I rather suspect that the cars that do have problems have a cut price engine management system.
which fuel (petrol) - corblimeyguvnar
a few years ago er indoors had an old metro which whilst running on shell 4 star, then LRP ran like a dream (apart from the clutch of course but thats another story)
they built a new tescos up the road so as it was cheaper i tried it out for a month, motor played up pretty soon and then bosh, piston ring stuck, could this be the 'poorer' quality fuel or just a coincidence?

Drink Lager Talk Piffle
which fuel (petrol) - hootie
This has all got me totally confused. I usually get my fuel at the supermarket because I'm there anyway (and because I usually get a 4p per litre discount ticket with the shopping, not to mention Nectar points)

There is a BP station in town though, and that gives Nectar points too, although not at the same rate as the supermarket's own station.

I do make an effort to put in fuel from a premium brand now and then, as I heard somewhere that you should make a change from time to time, rather than always using the same station. Or is that an old wife's tale?

I'm just wondering because of getting a new car soon - on a very small engine (1 litre) will it make any difference? and should we go with premium brands in an effort to cherish that little engine?
(comments gratefully received, but I don't want to start a war over it LOL)
which fuel (petrol) - tunacat
As Vin has said, there only seems to be anecdotal evidence. Some people swear by Shell, but I can't say I've ever noticed any significant and 'can't-possibly-be-attributed-to-any-other-factor' improvements in economy or performance with any particular brand - excepting the misfires noted at the top of this thread.

Shell came out with some 'special' petrol I forget the name of in the early 80's which later appeared to be damaging Vauxhall engines - allegedly. IIRC they had adverts in mags showing how it had been developed on a Vauxhall engine with a quartz window in it! So no brand may be immune to getting it wrong sometimes (fouling up?!).

One philosophy is "At least if I mix many brands into the slosh, I may be less at risk from the effects of any naughty ones."
Another is "Use Brand X exclusively - I'll be able to sue them if I can prove it's their fuel that's done the damage".

Take your pick!

Value my car