hi- most places in the u.s. & canada that i've been to that are pretty close to sea level usually have three grades 87, 89 & 92 or 93 [r+m/2 method]. some places are exceptions, like this one station i was in in missouri once that had five grades between 87 & 91 [i don't know why], or some sunoco stations out east that sell 86 octane 'economy' flavor [so you can save a whole penny over regular]. also, typically, as the altitude gets higher, the octane drops off slightly because the air is thinner and pre-detonation isn't as much of an issue. [the trick is to make sure you burn all of it before you come back down to 'normal' altitudes. ask me how i know...] i'm at around 500 feet above sea level here in chicago, and burn 93 most of the time in my bone stock '68 440. periodically, i'll top off with 89 if i've got more than 5/8ths of a tank left, and am yet to have an issue with pinging. i think a lot of it's subjective, though, and has to do with the car, the brand of gas, altitude, climate, et.c., but the general rule of thumb i stick with is burn premium fuel in a truly premium automobile. of course, with gas prices creeping up here in the states, i can empathize with what it must be like in europe... take care, --jason jason reizner chicago 68 crown hardtop >Hi, i just wonder what are the different octane >number gazolines you have in USA ? I know that >the US octane number is different than french >(RON) number and seems to be (RON + MON) / 2, so >a 98 RON (= 88 MON) would be a 93. At this time i >run my '57 Imp with unleaded 98 RON (so 93 for >you) and i want to switch to 95 RON ( = 90 US >gazoline, don't know if it exists..). __________________________________ Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month! http://sbc.yahoo.com