The winter blend differs from summer 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.
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.
There is one downside to winter blend gasoline, though. It contains more oxygen than the summer blend and that can negatively impact gas mileage by up to 3 percent, according to Chevron.
The average price of gasoline in Central Indiana is $3.66. That's about 7-cents more than it was in August and still more than $1 more than from this time last year.