whats the best petrol for a subaru legacy gt 1994 twin turbo boxer engine because l heard 98 octane is not very good for it so is 95 octane good or is 98 octane good aswell

Octane measures the gasolines ability to resist knock. In a hot turbo engine detonation/preignition can be catastrophic, you can get away with it but listen for any telltale pinging under load.

the higher the number the better. you get more power and more miles per tank of gas, it costs more but worth it. the lowest l would go is 93 octane.

91 is the call for all Subarus.

higher octane permits an engine to deal with heat, it does not add power. extreme heat can cause pre-ignition (resulting in possibility of engine knocking or worst case for performance engines piston or valve damage) & higher octane resists that as it ignites at higher temperatures.

engines with forced induction (either turbocharged or supercharged) r subjected to much higher levels of heat/stress when the forced induction system is engaged at WOT - wide open throttle.

you should run the level of octane ur car has been tuned for - 98 certainly will not hurt it, but its likely with a twin turbo it has been tuned for 93 or 94.
running too low an octane on a performance engine is dangerous as it subjects the engine to a chance of failure, running higher octane simply adds a measure of safety in the event u go to turbo.

my car is tuned to run on 94 octane (whipple supercharger running 15lbs boost), but occasionally l will add boost enhancer to run 98-103 octane

cheers, 04 cobra, measures 575rwHP on dyno
http://mustangattitude.com/cgi-bin/showcar.cgi?type=lot&pic=/2004/2004_00006_04

'' because l heard 98 octane is not very good for it '' you heard wrong.