Could someone please educate me. Having once had a nasty experience in my old STi Type R import (blown engine, 3 pistons/crank etc) I was told it was down to the ECU not being able to cope with our fuel (Ron rate too low) and the engine detonated itself, I was actually flat at the time so it was quite scary. I now own a UK STi8 and have been told by the dealer that there should be no problem as the ECU is programmed to run on 95 Ron (although I still pour Optimax down her throat). Is this correct or like the song says "there may be trouble ahead"? I intend to use the car as it was built for once run in so any advice to the contrary would probably save it spitting the dummy out all over again. Cheers Guy's an Gal's.

Ady

 

Sti8's cannot run correctly on 95 ron fuel. It says on the fuel flap to only use super unleaded 97 ron as a minimum. Stick to the optimax and next time you are in the dealers point this out to him. What dealer is this? because there muppets.

 

Thats odd Andy,

My filler flap has 'unleaded 98 ron fuel only' on it, not 97. However the Subaru brochure specifies that the car runs on 95 ron.

I believe the car can run on 95 with no damage, but can only obtain maximum performance on 98. Does anyone know different. Would be an interesting case if an engine failed, with the filler flap specifying 98.

I asked my dealer to clarify this with Subaru, and he stated that the car can run on 95, but not sure if he ever actually asked anyone.

 

Hi,
I have a STI8 and got advice from a friend who has run a number of Scoobs and he recommends using Optimax or any high RON fuel in them but the car should have no problem with occasionally running 95 RON. I stick to Optimax but have put normal unleaded in it with no problems.

 

Thing is, as a UK car it should be able to run totally on 95 with no damage from detonation but with less performance.

 

Cheers guy's, I am going to use Optimax anyway as I always think more octane more performance. Det does seem to be a big problem though with the scooby engine from what I have read and must admit much as I love the car I considered other options due to this, problem is where do you get that addictive thrum of a flat four cos I have never heard it replicated like the scoob motor! By the way my dealer probably read it in the brochure too about the 95 Ron fuel.

Ady

 

I have a my97 and that says on fuel flap... Use only unleaded super. Which I take to mean 97 Ron so I use Optimax. But if I can't get optimax, I try to get to a BP garage and use unleaded super but never use any 95 ron.

By the way STI8's are the dogs aren't they..

 

I went through all of this when I bought my STI 8. What I was told by a Subaru speciallist is that you can run on RON 95 occasionally but it is recommended to run on RON 97 or above. The higher the octane fuel the faster it burns in the cylinder under compression. Therefore the "bang" occurs in the centre of the piston with high octane fuel which is faster burning and is spread across the piston with lower octane fuels because they are slower burning possible causing damage.

 

I was also curious about what fuel to use and found that the manual explains it all.

IIRC it says that 98RON is ideal but 95RON can be used but Performance will be affected.....or words to that affect.

 

Optimax all the way guys, dont bother with anything else .....BP ultimate is ok as well though

 

Ady, welcome aboard mate, finally!! stick with the optimax & no driving with those deep sea diving boots on mate

 

TVR, the problem is not about sticking to Optimax, its the situation when you are empty and 95 is all you can get. In that case, it is safe (I believe) to fill with 95 and to drive normally.

If you want to know about detonation, try here More Than You Ever Wanted to
Know About Gasoline

 

At last - you found the on button for your computer

Happy posting.
Chris

 

Cheers guys, some useful info there, put my mind at rest. Thanks for the welcome Andy/Chris, yes it took me a while to pluck up the courage to post but now the bug has bit and the wife is tearing her hair out (I'm sure she thinks I'm sneaking off upstairs for a wafty crank!!!). See ya later guys.

Ady

 

having recently purchased sti8,i queeried my dealer about the 95-98 ron saga.ok to run on 95,the ecu will adjust itself,ie. recalibrate air/fuel mixture.recalibration will only take place under full load(max boost)conditions.sadly i will have to wait until first service.

Del

ps have also queeried poor cold start.dealer says,its an sti problem-they all do it!