So Optimax does go off!

[Turbo T]

Well had a rip today. My car has had a tank of the same Optimax in since I went to Surrey rolling road at the beginning of December (Now half a tank). During the spirited driving, my car went flat. You could hear the change in the exhaust note, and the boost was dropping by 6-7psi. The upshot is that the Optimax appears to have gone off to the point where the knock sensors picked up detonation, and started closing the fly by wire throttle down.

I will add some octane booster during the week to prove the point, but you have been warned. On a less complex EMS the results could have been a lot worse that just the throttle closing down.

[Turbo T]

I had been told before that it goes off pretty quickly, but never gave it any real thought. Live and learn.

[tuttle]

Turbo T said:

I had been told before that it goes off pretty quickly, but never gave it any real thought. Live and learn.

Have also heard this. The tesco 99Ron doesn't appear to suffer from the same level of degredation.

[LuS1fer]

I thought all petrol goes off. Doesn't the octane rating drop at a fairly alarming rate? I was using Optimax but couldn't get any so filled with BP Ultimate. After a month in the garage, the initial cold use of the car resulted in embarrassing kangarooing. Now the clutch on the Mustang isn't the last word in smoothness so it was difficult to separate clutch from fuelling but when warm, it improved. Having used the BP and refilled with Optimax and using the car daily, the kangarooing has stopped (I think..)

[stew-typeR]

it will drop off a little bit, but it wont drop as low as a normal unleaded fuel.

[iaint]

According to Evo's fuel test the bits that they use to make fuel higher octane tend to degrade quickest. They add stuff to slow the process but can't stop it entirely. From their test it seemed that Opti goes off quiker than Ultimate but it's also largely a factor of how busy the station is. Always buy from a busy forecourt!

[gofasterrosssco]

I pretty much always use Optimax and I have the same view that it does indeed 'go off'. My car is a Jap Import, so should be used to nice high RON stuff in its native land. Anyway, its odd because sometimes I fill up and the car is noticably smoother, keener to rev and with better torque, but other times it just isn't there.... and this is from the same garage.

I did quiz the little old lady at the station the other day about their frequency of fuel drop-offs, as I know its a pretty busy garage. She seemed bemused when I stated that I think it might 'go off' according to what I've heard and she laughed. She probably suspected me of being a terrorist for asking when they got their fuel delivered......

So from experience, it does appear to degrade slightly.....

My 2p

[LuS1fer]

LuS1fer said:

I thought all petrol goes off. Doesn't the octane rating drop at a fairly alarming rate? I was using Optimax but couldn't get any so filled with BP Ultimate. After a month in the garage, the initial cold use of the car resulted in embarrassing kangarooing. Now the clutch on the Mustang isn't the last word in smoothness so it was difficult to separate clutch from fuelling but when warm, it improved. Having used the BP and refilled with Optimax and using the car daily, the kangarooing has stopped (I think..)

To update, the car was perfect today and the clutch perfectly normal so I'm inclining to the view that the petrol had gone off standing round for several weeks and the fresh Optimax has sorted it.

[timmy30]

Fuel does 'go off' as you say, though I'm not sure you'd necissarily notice any difference in a practical sense. Lots of other variables, such as okay you left your car sitting in the garage unrun for a month...... yess I'm not suprised it took a while to wear back in. Not necissarily the fuel though.