Cars using summer-blend gasoline spew fewer harmful emissions and get slightly better fuel economy than those using winter-blend gas during the summer months.

The difference between conventional summer- and winter-blend gasoline has to do with the Reid Vapor Pressure of the fuel. RVP relates to the volatility of a gasoline. The more volatile a gasoline, the more likely it will evaporate as the temperatures rises; evaporated gasoline contributes to unhealthy ozone and smog levels. Summer gasoline has a low RVP and is less likely to evaporate when compared to the high RVP winter grade. The Environmental Protection Agency says conventional summer-blend gasoline contains 1.7 percent more energy than winter-blend gas, which contributes to the summer blend’s slightly better gas mileage.

The Energy Information Administration says the switch between the two fuels happens twice a year, once in the fall (winter blend) and again in the spring (summer blend). Summer-blend gasoline is typically more expensive to produce than the winter blend, and it won’t affect vehicle performance or the durability of the engine and fuel system, according to the EPA.

In many large cities as well as California and New England, the EPA requires the use of reformulated summer- and winter-blend gasolines. These RFGs contain oxygenates that lower RVP and other toxic chemicals even further than conventional gasoline.

Learn more

Answered by Colin Bird on February 18, 2009 in I'm Just Wondering | Permalink

Search Results

Ask.cars.com Search Results for

Search

See if your question has already been asked and answered

Thank You!

Your question has been successfully submitted to Ask.cars.com. It will now be reviewed by our editors and we'll answer it soon if we think it's a useful question. You will be notified via e-mail when the answer is posted. Ask.cars.com tackles your questions about new cars and the car-buying process. Unfortunately we can't answer questions regarding:

  • Used cars.
  • Most aftermarket products.
  • Mechanical issues. You can visit our friends at Car Talk to discuss your mechanical problems.
Thanks for your interest.

Ask

Have our experts answer any of your questions about new cars.

Email us at [email protected]

Maintenance Advice
Get answers from the
Car Talk Community