A Winter Storm Is Coming. Why When You Fill Up on Gas Matters

As a winter storm moves in, drivers often hear the same advice: Fill up when it’s cold. Keep your tank half full. Pump slowly to avoid wasting fuel.

But how much of that advice actually saves you money — and how much is just a myth?

While winter weather impacts driving conditions and fuel consumption, many popular gas-saving tips resurface during storms despite having little impact at the pump.

Is it better to pump gas in the cold?

Maybe you’ve heard this tip before: Fill up your tank when it’s cold because you’ll get more fuel for your money. Gasoline expands and contracts with the weather, so when it’s colder outside, the fuel is denser and you get more bang for your buck.

While that is scientifically accurate — temperature does affect the density of gasoline — here’s the catch: The fuel you pump isn’t sitting out in the cold like you are. It’s stored in underground tanks where the temperature barely changes, usually around 50 degrees year-round.

According to a study done by Consumer Reports, even if your local gas station did subject its massive stores of fuel to the elements, changes in temperature have a minimal affect on volume — only a few cents different.

If the temperature doesn’t vary, neither does the density, and you may be getting unnecessarily cold if you pump gas only when it’s freezing. Whether it’s morning or night, summer or winter, the fuel temperature — and the density — is basically the same.

What drivers should do instead during winter storms

Some people fill up whenever their gas tank is half empty. Maybe this is habit, or maybe it’s due to range anxiety, even in a gas-powered car.

Other rumors have swirled that it is financially sound to fill up on half a tank to prevent splashing and vaporization (and therefore wasting) of gasoline.

But, filling up to around a half-tank is good practice, especially during winter storms or when the temperature drops, according to Adrienne Woodland, a spokesperson for AAA of Michigan.

“We advise drivers, especially during the winter, to keep their tank about half full,” Woodland said. That advice is for safety, in case of an emergency, and not for superstition or worries about vaporizing gasoline.

Running on empty is also not good for your car’s longevity

Inside of a gas tank is a small mechanism called a fuel pump. The fuel pump is responsible for ushering along gasoline from the tank, through the fuel lines, and into the engine where it is combusted and turned into horsepower. The fuel pump relies on a constant stream of gasoline to run through it, which lubricates the pump and bearings and keeps it cool.

If you’re running on fumes, that could lead to a dry, overheating fuel pump. Replacing that costs more than a couple tanks of gas.

If you run out of gas in an emergency, don’t sweat it. But regularly driving your car till the fuel light pops on is probably a bad idea. For that reason — not because of vaporization or range anxiety — it’s generally a good idea to fill up when you’re down to a quarter of a tank to make sure, you’re not putting any excess strain on your fuel pump.