Which Petrol to use? Advice please

fivetide

artbaron wrote: »

I know two people who blew their Subaru engines because they used 95 RON. The first guy is a Subaru mechanic and blew the engine on the track after chancing it with 95 fuel for the first time. The other bloke was my neighbour and after two tanks of 95 RON his new £40K WRX gave up the ghost and left him with a 5 figure repair bill which was eventually paid on warranty but not before arguments over him using incorrect fuel.

A standard WRX from the bugeye shape (2001?) onwards will not det on 95 fuel. It will run slightly less power but it will run fine. As Nev said, you couldn't get a 40k WRX so it would be a STi minimum and then possibly a special edition.

If you've tuned the car at all and haven't had it properly mapped for fuel and you are thrashing the nuts off it on a race track then you are asking for it to go pop!

Jamie_Carter

I don't know if this is still the case, but supermarkets used to use the lowest possible legal standards for their fuel, and used to boots the octane with butane.

A mechanic friend told me this a while ago: A guy bought a brand new Mercedes, and shortly afterwards goes on a summer holiday, leaving his car at the airport. On return his car wouldn't run properly, so he took it to the Mercedes dealer. They tried everything, but couldn't get it to run properly. So they asked him what fuel he used, to which he replied "supermarket fuel". On hearing this they drained the fuel out, and refilled it with new fuel, and the car ran perfectly.

What had happened was the butane used to boost the octane had evaporated in the summer heat whilst parked at the airport. So the octane level had lowered.


The mechanic friend told me the above after my old Astra suffered pre-ignition (the fuel/air mixture igniting before the spark plug sparked) whilst driving up a long steep stretch of the M62. The pre-ignition was caused by carbon deposits on the spark plugs. He guessed that I used supermarket fuel as soon as he saw the plugs.


However he didn't say that I should avoid using supermarket fuel altogether, he just said that I should use one of the big brands for every fifth or sixth fill up, which would help to clean up any carbon deposits.


As for the higher octane fuels. Fifth Gear did a test on this. And from what I remember there was no advantage financially for using high octane fuels.

fivetide

V-Power also degrades. It can be anything from 98 to 100 RON depending how fresh it is. That's why Shell don't put a RON figure on the pump if you notice... Tesco however are happy to say their super stuff is definitely 99 RON so make of that what you will!

Jamie_Carter

fivetide wrote: »

V-Power also degrades. It can be anything from 98 to 100 RON depending how fresh it is. That's why Shell don't put a RON figure on the pump if you notice... Tesco however are happy to say their super stuff is definitely 99 RON so make of that what you will!

Could it be that Shell also use butane to boost the octane? And maybe Tesco only claim it to be 99 RON when sold?

fivetide

Jamie_Carter wrote: »

Could it be that Shell also use butane to boost the octane? And maybe Tesco only claim it to be 99 RON when sold?

That I don't know. Apparently Tesco 99 is very good stuff and quite respected by the tuning types.

I think the very instability of V-Power is part of what is meant to make it work but again, back to the ECU thing, it takes ages for a car to adjust to the fuel (if it even has that ability) and generally you mix it with whatever is in the tank so anyone claiming they can feel a boost as soon as they leave the forecourt has a case of Emporer's new clothes syndrome!

oldhenry

Some people believe advertising and some do not. Twas ever thus and there will always be suckers so there will be advertisers. All petrol sold has to be to a British Standard - the RON and the car manufacturer specifies which your car requires in the handbook. So read that and fill up . I have kept records of my vehilcles since purchsed and what fuel they have had and over 100,000s of miles there is no evidence of a different fuel either givinng more economy or of ruining an engine. Stick to teh BS for your car otherwise it is a waste of your money.

Paradigm

Jamie_Carter wrote: »

Could it be that Shell also use butane to boost the octane? And maybe Tesco only claim it to be 99 RON when sold?

AFAIA Butane isn't an octane booster but is added to aid starting a cold engine, particularly in winter, due to it's low boiling point.

chunkychocky

I fill up my 2001 VW Polo TD once the red light comes on (always have done from it being new). With Tesco diesel I can do 410-420 miles on a tank, Shell ordinary diesel I can do 420-430 miles on a tank, and Shell Nitro+ (or whatever the new stuff is called) I get 450-480 miles on a tank. Speaks for itself as far as I am concerned. Interesting that not everyone finds similar results.

Jamie_Carter

chunkychocky wrote: »

I fill up my 2001 VW Polo TD once the red light comes on (always have done from it being new). With Tesco diesel I can do 410-420 miles on a tank, Shell ordinary diesel I can do 420-430 miles on a tank, and Shell Nitro+ (or whatever the new stuff is called) I get 450-480 miles on a tank. Speaks for itself as far as I am concerned. Interesting that not everyone finds similar results.

The only way to get an accurate result is to compare several tanks full of fuel for each type, and find an average for each particular fuel. Then take into account the different prices for a tank of each type of fuel.

chunkychocky

Jamie_Carter wrote: »

The only way to get an accurate result is to compare several tanks full of fuel for each type, and find an average for each particular fuel. Then take into account the different prices for a tank of each type of fuel.

Yes I have done this too. The 'more expensive' Shell fuel works out cheaper than the others per mile. The VPower Diesel worked out at approximately the same price as the Tesco fuel per mile (a tiny fraction of a penny less per mile for the VWPower, but really so insignificant as to just be splitting hairs), but the newest fuel really does seem quite a bit cheaper per mile. I've only used it for a few tanks though, and I know fuel efficiency deteriorates in the winter so it will be interesting to see what happens then.