Should you use premium gasoline in a Harley-Davidson? – Jalopnik

Although Harley-Davidson motorcycles were once the domain of scruffy counterculture types and even gang members, owning a new Harley today requires a deep wallet. The least expensive of the classic ‘big twin’ range, the Street Bob has an MSRP of $15,999 without options. That can easily top $45,000 for a top touring bike like the CVO Road Glide ST or the $110,000 limited edition CVO Road Glide RR that lets you pretend you’re competing in your 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 V-twins bring between 98 and 153 horsepower to the party. To achieve this, a fairly high compression ratio between 10.3:1 and 11.4:1 is used. That, friends, calls for premium fuel. And indeed, a quick look through the official Bar and Shield user manual confirms as much; Every new Harley we examined requires a minimum octane rating of 91, including the brand’s Revolution Max-powered models like the Sportster S and Nightster.

So far we’ve discussed the octane ratings of new Harley-Davidson products, but what if you own an older motorcycle, such as one with a twin-cam engine that ran from 1999 to 2017? Know that the owner’s manual for those years also specifies gasoline with a minimum of 91 octane. By the way, if you can’t find the owner’s manual, Harley offers an online copy – along with loads of other useful information – on its website Service information portal.

In the past, Jalopnik has written extensively about whether or not to use premium fuel, so we’re not going to summarize all that material here. Suffice to say, on high-performance, high-compression engines, premium gas prevents the knocking and knocking that can damage your engine. That said, modern engines have sophisticated computer controls that detect lower octane fuel and adjust ignition timing and sometimes other factors to prevent such damage. However, this protection against lower octane gasoline will hinder the engine’s maximum performance.

According to AAApremium fuel costs an average of 86 cents more per gallon than normal. When you pump 20 gallons into your car or truck, that equates to about an extra $17 for premium gasoline, which is not insignificant. On the other hand, motorcycles have much smaller fuel tanks and tend to have much better fuel economy than most cars and trucks, so fueling your motorcycle with the best can cost less than a specialty coffee.