geting a bit sick of so called experts saying you do not have run a import on superunleaded or optimax with booster.
what is the gen come on there must be a definate answer?

 

No such thing as a definite answer as no two cars are exactly the same. The safest (convenient) combination you can run is SUL/Optimax along with booster and that is the minimum I'd run any Jap import on.

 

Neil.
If you are running an Import WRX.
I would strongly suggest you run it on OPTIMAX and booster (These cars are built for the Japanese market to run on 100 ron fuel).
It would be fair to say that the ECU may be able to adjust itself to run on say OPTIMAX alone .
But performance loss would result .
Failing of a MAF. sensor in this condition. (All too common. As owners can testify). would cause under fueling resulting in detonation and at least a melted piston.
Would recommend OPTIMAX, Booster and a Knocklink as a statutary reqirment for any Jap import. (Unless re-mapped to run 95 ron fuel like much slower UK car)

Believe me I've been there and it isn't fun!

 

Me too... USE BOOSTER AND GET A KNOCKLINK !!

 

I run Optimax only, or SUL if I can't find any, and I've never had any problems in five years and 120k miles running twin-turbos (Legacy RS-B and Galant VR-4) without octane boosters. Octane booster was reckoned to be the cause of a contaminated lambda sensor on my Legacy, so I stay away from them now.

 

H7,

But that's a Legacy and not a japanese Impreza. You can't compare two different cars that run different ECU's and mappings.

Don't listen to these so-called experts unless they'll guarantee to pay for the new engine if it does let go. Some cars could run without booster, but it depends too much on how it's driven and how susceptible it is to detonation.

If you're going to do anything, then air on the side of caution and run Optimax or SUL with some booster.

Get yourself a Knocklink so you can see if it is detting or not.

Stefan