I took my car out for a run yesterday afternoon after leaving it in the garage for the last couple of weeks and noticed that at high revs and boost it was pinging. I always use BP Ultimate and have never had this issue before. The current tank of fuel has been in there for 5 to 6 weeks. Can fuel go 'off' that quickly?
Matty

Like most things now I'd say "Yes, yes it can". I just moved an old 2 stroke mower of mine and the tank leaked and you'd think it was water based red paint or something that came out

Yeah it will get water in it and thats what will make it go bad.

I was thinking about the water situation after I posted. Because the tank has been less than half full for quite a long time and the weather has been cold that would allow condensation to build up inside the tank.
Thanks for the responses guys.
Regards Matty

Gasoline can last years. I've started many cars using fuel in the tank that was at least 5 years old.

water in the tank doesn't cause pinging...

having been involved in racing for years, I've heard alot of stories like this of cars pinging after being left to sit for a period of time with optimax in the tank. fresh fuel fixes the problem.

common wisdom is that optimax (and other 98RON fuels) have a relatively short shelf life of around 3 weeks before the RON drops significantly.

the official word from shell is somewhat non-commital. They say the fuel will be stable if stored up to one year, as long as the storage conditions are "adequate" - ie the containers are full to minimise exposure to air, tightly capped, out of direct sunlight, and under 27

Thanks Harry.
I generally fill the tank more regularly as I usually drive the car more. I'll fill it up tonight and see if that fixes the issue.

fuel lasts for months get it checked i dont think it would be your fuel

have you looked at anything electrical? i think it might lie elsewhere too.
but buy a tank of fuel first.

Ive always heard that gas goes bad after sitting for about a month. I dont think its water that makes it go bad(although if theres water in it thats not good). What happens is the unstable gasoline molecule breaks down and degrades over time. It can still run in an engine but ive read that it breaks down into a chemical that can ruin fuel lines and rubber seals.