I have a Evo with 10.0 compression and I have to run 93 octane. If I can't get it I have to break out the octane booster. Rattling valves makes me uneasy.
I only use 98 Mobil or Caltex... after I got Emma Dyno'd the bloke recondened shell is crap.. after 10 years and heaps of tune ups I AGREE...
we're pay'n $1.40 a litre atm