Gas prices are nearing the $4 mark once again.
One reason for the recent increase is because refineries are rolling out their summer blend.
The summer blend differs from winter blend varieties because of Environmental Protection Agency regulations about the Reid Vapor Pressure of the fuel. RVP refers to how likely gasoline will evaporate. Refiners are required to adjust RVP levels to comply with emissions regulations depending on the season.
Refiners adjust the process to decrease the RVP levels in the summer. Summer gasoline has a lower RVP level so that it doesn’t evaporate, emitting more smog in extreme heat. The lower RVP requirement makes producing the summer blend more expensive, therefore making it more expensive for consumers.
Despite the higher cost per gallon, drivers will see up to a 3 percent increase in gas mileage, according to Chevron. This is because the summer blend contains less oxygen than the winter blend.
Most cities start rolling out the winter blends with a higher RVP during the middle of September. Because lower temperatures mean a lower chance of gasoline evaporating, the fuel does not have to be as refined as the summer reformulated gasoline. Less refining means less cost for production and therefore lower prices for consumers.