Subaru fuel type.

[MK4 Slowride]

I've been using 98ron as the car wants but how much difference would 95ron make and if the previous owner had been using 95ron would it take long for the car to adjust back to 98ron?

[markCSC]

As you have a 2.5 with PPP, I wouldn't put anything other than 97/99 RON in it. One of the Forester guys ran his 2.5 PPP on 95 ron and it was soooo slow. he thought it was broken. He spoke to Prodrive who said

"By using 95 RON the ECU will disable the soleniod valve that controls the turbo boost. Basically make it run as a non-turbo engine."


If it has been run on 95 Ron, disconect the battery for a couple of hours to reset the ECU.

[Dibs]

Yep, according to Prodrive "To obtain maximum benefit from the package, we recommend continued use of Super Unleaded
(97 RON) fuel.", so you will see a drop-off in performance if you go back to 95.

See the datasheet for full details.

Dibs

[paulmoonraker]

I am not sure it won’t come on boost if you use 95ron. I have used that before in a WRX PPP and it will boost, but there is a slight lack in performance. The engine is mapped for high octane fuel, so using a lower octane will reduce performance. Long term is may also cause other issues, but (I think) the knock sensor should help limit damage by retarding the timing etc... The performance difference on my old WRX was noticeable, however, in my STi it is significant…

You cannot reset the ECU on a new age by disconnecting the battery. You need to either download ECU explorer and get a cable (what I did), or just wait for the ECU to learn that you are using higher octane fuel.

HTH