H-GOOD QUESTION

Jun 20, 2013 1:54 AM by John Reger

GQ: What's the difference between winter and summer blend gasoline?

One of the reasons gas prices are going up right now is that refineries switch from gas they make for winter to what they make for summer.

L.N. from Santa Maria asks: What's the difference between winter and summer blend gasoline?

Gasoline has ingredients that evaporate more as the temperature outside gets hotter. This evaporation causes more smog. To cut down on pollution, refineries cut down on the ingredients that burn off more quickly in summer.

Most winter blends use more butane which is cheap and plentiful, so gas prices are lower. But butane evaporates easily in heat so it has to be replaced by other ingredients which are more expensive. Summer blends get slightly better gas mileage.

Different states and cities have their own rules for blends based on their seasonal temperatures, and they have different times for the switchover.

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