Hey Guys, I filled up with the optimax extreme on saturday. Had one click or 2 worth of vortex 98 when i filled up. I have done 180Km's city driving since then and its smack bang on 3/4 of a tank. Thats a record for me on any fuel. I spoke to the mechanics at dads work and they say 5% enthonol can be good for alot of things, i.e keepign the tank clean so forth. The engine feels like it is sparkin quicker then the vortex 98 as well with a smoother mid range feel to it. Anyway thats my 2 cents. -Bill