Quote:
Originally Posted by redpoint5
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.
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I was wrong, I went and looked it up, it is different. It's just most cars can get away with it at altitude. I know I've always ran it in all the cars I have ever had and never had any problems. I bet you could actually get away with it in most cars at any altitude, so I'm glad I at least get a choice. I read in Colorado still 80% choose 85, and about 10% chose 87 and 10% choose 91. If you just are driving normal in a normal car saving $.10-15/gallon is great especially at these low prices. When it goes to $4/gal then it still seems to be at same $.10/gal extra for 87 but it doesn't seem like that much extra.