techincally, carrying a thicker head gasket would get you a lower CR, but you dont want to be swapping that around for a tank of fuel Easier to retard the timing if there was a problem, I think. Like you say though, it really depends on where you think youre headed. I've never had to buy gas out from a hand pump in a barrel, or a soft-drink bottle, yet, but they are out there, deep in Mexico and Cambodia. I would think fuel contaminants would be a way more frequent thing, like water or just crap, and not the octane rating. Hell, its almost impossible to find Leaded fuel anymore, and I've never heard of anything below say, 85 or so.