Dear Mr. Know-It-All,
I can’t remember a time before your column was in Dirt Bike, and I have been a reader since before Super Hunky left, yet I have never before asked a question. What is the order of preference concerning fuels? Should I use 89 octane with no ethanol or 91 and 93 octane with 10-percent ethanol? I ride a 2012 Husaberg FE390 and a 2017 KTM 350SX-F.
via [email protected]
Dear John, I contacted Jeff Slavens, for his take on the ethanol issue. If you ride at high elevation—above 5000 feet—the need for octane is greatly reduced. As you climb up the mountain, the air gets thinner and the engine compression gets lower, therefore high octane is not needed or beneficial. If you’re a flatlander, octane makes the engine run cooler by slowing the flame front and making the jetting slightly richer. For low-elevation riding, go for the 89-pump fuel and add an octane booster. Maxima, Spectro, Lucas offer boosters that will get your fuel up to 93–94 octane.