Summer gasoline map
It’s no secret that the annual climb in gas prices that accompanies the transition to ‘summer blend’ gasoline rattles many cost-conscious consumers... but there’s also no denying the benefits both visible and invisible.

“It’s important to remember why it began,” said Patrick DeHaan, senior petroleum analyst with GasBuddy.com. “The summer gasoline requirement was a critical part of the Clean Air Act. It was approved with overwhelming support by Congress and signed into law by President George H.W. Bush in 1990. At the time, the three major environmental threats were acid rain, urban air pollution, and toxic air emissions. That’s why the Environmental Protection Agency (EPA) regulates the volatility of conventional gasoline sold at retail stations during the summer smog season (June 1- Sept. 15) to reduce evaporative emissions that contribute to smog.”

Reformulated Gasoline (RFG) was mandated for those metro areas with the worst smog beginning in 1995. It’s blended to burn cleaner than conventional gasoline, reducing emissions of smog-forming and toxic pollutants.

“By reducing the volatility of the summer gasoline, which is measured by the Reid Vapor Pressure (RVP), we also reduce emissions. (Summer blend gas has lower RVP than winter gasoline.) How important is that? Just think back to the air pollution we all saw during the Beijing Olympics of 2008... that’s what some of our cities might look like if we didn’t have these regulations,” added DeHaan.

Mileage improves, slightly...

“If you want to see the invisible benefits just check your mileage. You should see a slight improvement. Cars like warm weather a lot better than the punishing cold. Winter gas contains more butane and the fuel diluted with ethanol and/or butane typically lowers fuel economy by 1 to 3% due to lower energy content. Gasoline sold in warmer months has a higher energy content which results in better gas mileage,” DeHaan noted.
“Of course, in warm weather your engine reaches normal operating temperature faster so fuel economy improves. Heat reduces your oil’s viscosity and that reduces drag on the engine and increases your gas mileage. Your car’s engine operates more efficiently when the oil flows like water, not sludge.”