I have a 2005 WRX which has been remapped to 283bhp (Scoobyclinic) and have ran it on Shell Optimax ever since.

However, my local Shell was out of bounds on Monday and the fuel light came on so I had to put £10 worth of Jet fuel in and the car ran absolutely fine. Later filled it up with BP Ultimate and the car has been running on that for the past few days.

Just wondering now whether I could fill it up with normal unleaded as the £10 of Jet fuel was absolutely fine (and cheaper). Would this cause long term damage though???

 

The best you should use the fuel your car has been mapped to. Or better- in this case higher octane number.

 

if you run it on lower octane fuel you run the risk of det which will end up destroying your engine,run it on the fuel your car has been mapped for.if you do get caught short and have to put lets say not the correct fuel in you may run it but no hammering and deffo no boost,steve

get some octane booster in the boost just incase yopu get caught short again

 

Using cheap fuel will be fine if you dont run at high load/boost.

As stated above it will no doubt cause damage if you run at prolonged load/high boost.

I wouldnt think twice if I had to use it to get me home. You just need to be sensible about it.

 

Like 172Sport said, you're unlikely to have any problems unless you cane it.

However, just be aware that among the many systems in the ECU are Dynamic Advance and Feedback Knock Correction. If the fuel you put it causes knock due to the low octane rating then ECU will register this and retard the ignition advance to compensate automatically. I have megabytes of logs demonstrating this on my 05 STI. Basically your car is going to remember that you were a tight b*****d and didn't give her the v-power she likes so she isn't going to put out for you when you mash the throttle...

Fortunately, if you empty the tank and fill her up with the good stuff it will take between 50 - 300 miles (depending on how you drive) for her to start trusting you again and uncross her legs, i.e. the ECU will progressively start to clear the knock correction it recorded.

 

A bit strange this.

Your title reads : Normal Unleaded petrol in an STi???
Then you say : I have a 2005 WRX

Then : and have ran it on Shell Optimax ever since.
And then : £10 worth of Jet fuel in and the car ran absolutely fine. Later filled it up with BP Ultimate

So is it a WRX or STI and why not put in Shell later on, rather than BP?

 

Mine is a 2005 WRX STI Pro-drive, like it says on the back of the car. What's the issue with it?

I agree with not using BP. That 'Ult' crap causes me problems. However I can use Tesco 99 in a pinch. Doesn't say much for BP.

 

Sorry for the totally misleading title.

The car indeed is a standard WRX remapped (its just that it has the STi bodykit and stickers on). My bad.

I put £10 of Jet fuel in and then passed a BP and thought better fill it up with some super-unleaded as I was a little cautious of driving with normal unleaded. The next Shell petrol station is around 4 miles away from me and didn't fancy driving the car too long with normal unleaded in.

Also noticed that BP's Ultimate is 97 ron. Is this lower than Shell's Optimax?

 

Yes shell is 99.
I have ran mine on 97 instead of 99 but I do have a KS3 to keep an eye on whats happening. I do carry methanol as well to boost the 97 should I have to use it, only a 5% mix though nothing more if it isn't mapped for it. The mapper said it will be fine on 5% but thats it.