MPG better in summer?

I have a 2000 Chevrolet Cavalier and a long commute. I have noticed I get 30-32mpg when the weather is warmer and only 27 - 29 when the weather is colder. No change in driving style, can this just be temperature related? I have been told the gas formulation in summer is different from winter, is that true and would it make that big of a difference?

Yes And Yes (The Formulation Is One Factor. Cold Weather Is The Other).

before we make assumptions, we need to know where you live, how far you commute, if change where you drive to in the winter, if theres snow on the ground, and if you drive slower in snow.

we cannot answer without these.

My MPG Has Already Started To Drop For The Winter. I Had 14F Degrees This Morning, Following The coldest October On Record.

besides the gas formulations, engines need a richer gasoline mixture at warm-up, grease and tires need to warm up to temperature to offer less resistance, and cold air being more dense offers more wind resistance in cooler weather.

You definitely should locate the recommended tire pressure for this vehicle and be sure to inflate the tires to this level. Once cooler weather hits, the tire pressure falls. I have to correct every car in my fleet this time of year.


That makes sense, thanks for the explanation. I always keep a good eye on maintenance but I don’t always gauge my tires. Good call.

Electrical loads tend to be more also, headlights, defroster, heater, wipers…None of this stuff works for free…

More butane and propane are blended into gasoline in the winter to provide quick starts and fast warm-ups. But they contain fewer BTU’s (energy) than pure gasoline…So it all adds up to reduced mileage…

one more thing. the gas you buy in winter is different then the stuff you get in summer.

in the winter formula, there is less ethanol, making it burn better in the cold.

summer stuff has a higher percentage of ethanol. if you fill up a car in winter, let it sit till july, and try running it, it will have tuning problems.

although in the southern states, it may all be the same gas year round.