Winter-Blend Gasoline Can Begin Pumping Sunday: RivCo, SoCal

RIVERSIDE COUNTY, CA — The average price of a gallon of self-serve regular gasoline in Riverside County rose three-tenths of a cent Friday to $3.124, one day after dropping one-tenth of a cent to its lowest amount since July 27 — and there could be more decreases in coming days and weeks.

The average price is three-tenths of a cent less than one week ago, 2.1 cents less than one month ago and 87.7 cents cheaper than one year ago, according to figures from the AAA and Oil Price Information Service. It has dropped 38.4 cents since the start of the year, including six-tenths of a cent on Wednesday.

"Southern California wholesale prices have dipped by more than 30 cents since Sept. 1, and with winter-blend gasoline on the way, there will be a lot of downward pressure on gas prices," said Jeffrey Spring, the Automobile Club of Southern California's corporate communications manager.

Stations can begin selling winter-blend gasoline, which is cheaper to produce, on Sunday.

According to AAA, the difference between summer- and winter-blend gasoline involves the "Reid Vapor Pressure" of the fuel. RVP is a measure of how easily fuel evaporates at a given temperature. The more volatile a gasoline (higher RVP), the easier it evaporates.

"Winter-blend fuel has a higher RVP because the fuel must be able to evaporate at low temperatures for the engine to operate properly, especially when the engine is cold. If the RVP is too low on a frigid day, the vehicle will be hard to start and once started, will run rough," according to AAA.

"Summer-blend gasoline has a lower RVP to prevent excessive evaporation when outside temperatures rise. Reducing the volatility of summer gas decreases emissions that can contribute to unhealthy ozone and smog levels. A lower RVP also helps prevent drivability problems such as vapor lock on hot days, especially in older vehicles," according to AAA.

Conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which is one reason why gas mileage is slightly better in the summer, according to AAA.

Summer-blend is also more expensive to produce, and that cost is passed on to the motorist. Motorists will begin to see summer-blend gasoline again in the spring.

—City News Service contributed to this report.