Do i really need to use super unleaded/ optimax and an octane booster in my 95 jap impor WRX, if so what's the crack with the octane booster ie how much do i put in per tank full of fuel.

 

Unless it's been remapped to run correctly on UK fuel, yes. Unless of course you want to run increased risk of your engine eating itself.

It would also be well worth fitting a KnockLink to guard against a bad tank of fuel, running out of booster, or your engine running a crazy Japanese chip.

You want to get hold of some NF Race Formula (ideally) or Millers. As for how much, there are instructions on the side of the bottle. Your car is expecting 100 octane fuel, so just work out how much you need to add to raise the fuel from 98 (Optimax) or 97RON (other Super Unleadeds). With NF it's something like 10ml of booster for every litre of petrol.

 

I use millers in my WRX import, 1 bottle when i fill the tank to the top.

 

Ive used optimax only for 2 years with no problems. I do have a AFR meter to keep and eye on the mixture, but ideally you do want a knock link..

Dan