Originally Posted by lagman
From my owner's manual:
"use unleaded gasoline. (octane rating 87 [Research Octane Number 91] or higher)"
So I assume I have a "premium optional" vehicle..
That's interesting. Clear as mud. The manual for my Chevy HRR and my past Cadillac both were very clear that they can run premium. Best you can do is run a couple of tank fulls of each without towing and see what your mileage is and how the power feels. It'll only cost you a couple of bucks to find out. I can tell you that when I run premium in my HRR I get slightly more power at freeway speeds and slighly better mileage. Enough to make it worthwhile so long as premium isn't more than .20 a gal more than regular.
Originally Posted by 3'senough
I have a flex fuel vehicle and the ethanol is worse on fuel economy as a direct result of power loss from it's burning vs dino. .
With 10% ethanol people see results all over the chart. I don't see much difference myself, but if you have a flexfuel vehicle and run E-80, there will be a dramatic difference in mileage, for the worse because of the lower energy output of Ethanol. Your manual will also tell you to never tow with E-80. However, all of this is academic, the OP is asking about Premium vs. Regular, not E-80.