While Harley-Davidson motorcycles may have once been the domain of scruffy counterculture types and even gang members, to own a new Harley nowadays takes a thick wallet. The least expensive of the classic "big twin" lineup, the Street Bob, carries a suggested price of $15,999 with zero options. That can easily balloon to more than $45,000 for a top-of-line touring bike like the CVO Road Glide ST or the $110,000 limited-edition CVO Road Glide RR that lets you pretend you're in your very own King of the Baggers race.
The good news is that as Harley prices have escalated, so has performance. For the 2025 model year, the latest Milwaukee-Eight series of V-twins bring between 98 and 153 horsepower to the party. To accomplish that, a fairly high compression ratio between 10.3:1 and 11.4:1 is utilized. That, friends, calls for premium fuel. And indeed, a quick browse through the Bar and Shield's official owner's manual confirms as much; a minimum pump octane rating of 91 is required for every new Harley we researched, including the brand's Revolution Max-powered models like the Sportster S and Nightster.
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So far, we've covered the octane requirements of new Harley-Davidson products, but what if you're the owner of an older bike, like one with a twin-cam engine that ran from 1999 to 2017? Know that the owner's manual for those years also specifies minimum 91-octane gasoline. By the way, if you can't locate your owner's manual, Harley provides an online copy — along with loads of other useful info — at its Service Information Portal.
In the past, Jalopnik has written extensively about whether to use premium fuel, so we're not going to recap all of that material here. Suffice it to say that in high-performance, high-compression engines, premium gas prevents knocking and pinging that can damage your engine. That said, modern engines have sophisticated computer controls that sense lower-octane fuel and adjust the ignition timing and sometimes other factors to prevent such damage. However, this protection against lower-octane gasoline will handicap the engine's maximum performance.
According to AAA, premium fuel costs an average of 86 cents more per gallon than regular. When pumping 20 gallons into your car or truck, that equals about $17 extra for premium gas, which is not insignificant. On the other hand, motorcycles have much smaller fuel tanks and typically get much better fuel economy than most cars and trucks, so giving your bike the best could cost less than a specialty coffee.
