Quote:
Originally Posted by Hersbird
I'm not positive how it works but I think that 85 octane is the same exact gas they sell at 87 in Washington and Oregon it just gets labeled the lower rating because of the average elevation
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That was the opposite of my understanding, that MT 85 is 85 PON, but it has similar resistance to burning at elevation as 87 PON at sea level. Lower atmospheric pressure > lower air density > lower compression heat > lower risk of detonation.
We all observe that the higher the octane rating, the higher the price of fuel, so my assumption is that 85 PON is cheaper to produce.
I run 85 PON when I'm in MT, but then I fill up with "premium" as I head out, prior to descending back to sea level.