gasoline types

It's true for any motor. The lowest octane you can run WITHOUT detonation (reguardless of compression) will make the most HP. It's pure physics. Of course the higher compression will require higher octane...that's to keep it from.....detonating.

 

ANY motor will make more power with lower octane as long as it's not detonating. That's the key....you run the lowest octane you can with no detonation. Up the compression...you'll have to up the octane.

 

"My bad, I was under the impression it was on the lines of 9:1. 10:1 i think is higher then Ive ever seen in a truck! Wonder if the math balances out or makes it most cost efficient to run the 93 rather then 87 in a 4.0?

This topic also has me wondering what the people above 3000-5000 feet are doing. Any 85 octane users???"

I live at 6000 ft and use 85. I have not noticed much of a difference between 85, 87, 91 but with some recent mods, intake and exhaust I think i'll move up and see what the break even point is for mpg and fuel cost for higher octane. It basically costs $4.00 more for the good stuff. At 3 tanks a month that is about $150 a year more. I think I'd rather pay the extra and have some peace of mind that my engine has the best fuel.

Like in those juice commercials - put good in, get good out.