Why Gas Mileage Improves in the Summer

There are significant environmental benefits to summer-blend fuel, as well as increased fuel efficiency.

June 29, 2018

ALEXANDRIA, Va. – By June 1, retailers in more than 30% of the country were required to sell summer-blend fuels. The annual spring transition to produce, transport, store and sell these fuels is one of the reasons that gas prices have increased an average of 53 cents per gallon each spring since 2000, when the Clean Air Act Amendments required that summer-blend fuels be sold in many areas of the country. Since 2000, many other areas have opted in to the program, and summer-blend fuels now are used in 18 states—largely those with more densely populated communities.

Summer-blend fuels evaporate less readily, so they are less likely to lead to the formation of smog in the warmer months. The downside is they’re more expensive to produce, and the transition puts enormous upward pressure on prices across the country as refineries are retooled while demand increases.

While the pain of this transition to summer-blend fuel is felt throughout the United States, there are significant environmental benefits. And there’s another key advantage for drivers: increased fuel efficiency. Part of the reason for the improved mileage is the makeup of the fuel itself, but weather-related factors also play a big role.

Regardless of where consumers fill up in the United States, they often will enjoy better fuel efficiency in the summer months. The level of fuel efficiency will depend upon fuel specifications required in certain regions, as well as weather-related factors.

To help consumers and the media better understand the transition to summer-blend fuels, NACS developed the “Why Gas Mileage Improves in the Summer” primer, housed at the online NACS Fuels Resource Center. Here, readers can find dozens of primers, white papers and infographics that help explain market conditions and the dynamics behind their fill-up from the industry that sells 80% of the fuel purchased in the United States.