Fuel power 60. Please allow me to throw out an anecdotal story about it. I have two big v-twin motorcycle engines that get FP60. One is 2053 cc's, and the manufacturer states to use 90 or higher octane, because of the pinging problems associated with these big combustion chambers. I run 89 Octane and the recommended 1 ounce per 5 gallon rate, and at WOT on much of a 7 mile hillclimb where it was 100 degrees at the bottom, (and the bike was well warmed up, as I had a 115 mile ride to get to the mountain) I get not one ping the entire time. Many people with this engine still report pinging on 93 Octane. I know FP60 is NOT an Octane booster, per se, but, something about it's qualities allows this monster engine to run just fine on lower octane. I'm thinking of trying 87 in it. I got 50 mpg on this trip with this big engine, including the hillclimb. Amazing to me. Maybe I'm just easily amazed.