DAYTON, Ohio -- As the weather warms people may find themselves filling up a bit less. That’s because cars are more fuel efficient in warmer weather.

“You can lose three miles to the gallon when it’s 20 degrees, and gain that three miles back when it’s 70 degrees,” said Douglass Jennings, manager of Tiger Auto Services in Dayton.

One reason for this is it doesn’t take as long for cars to warm up when it’s warmer outside.

Another reason has to do with the amount of oxygen in the air.

“When it’s hotter there’s less oxygen, and the car requires less gas to get the same fuel efficiency and power that you had before,” said Jennings. “That means your mileage will go up.”

When it comes to the weather, temperature isn’t the only thing that affects gas mileage. Those who drive higher-profile vehicles may find the wind also drags down the mileage.

“Oh, I’m sure there’s a lot of drag on the vehicle, so you’re not going to get very good gas mileage,” said Dave Tock, who drives a pickup truck.

No matter what size the vehicle is, as the temperature goes up, so does the tire pressure.

“The size of the tire will increase, when it’s cold, you’ll lose about 2 pounds of air pressure for every 10 degrees,” said Jennings.

That means the tire travels 2 inches less with every rotation, which uses more gas.

As the warmer weather sets in, the change in fuel efficiency may be small, but with gas prices this high, every little bit helps.