Is it better to pump gas in cold weather? Analyzing fuel saving myths

Chances are, you’ve heard tales of fuel pump etiquette framed as fuel- and money-saving tips: Fill up once your tank is half-empty. Pump gas slowly to avoid vaporization. In contrasting wisdoms, some say to pump gas when it’s warm outside to preserve your fuel lines, while others say pump gas when it’s coldest to save money.

But how much of it is true?

While there are an array of tips and tricks for saving a buck or two at the pump, some of these tidbits of advice are either outright false, apocryphal or only relevant if your vehicle is 40 years old. For the most part, the best way ‌to save on gasoline is to find the cheapest gas station.

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. 

Is it better to fill up when you have half a tank?

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.

Whatever reason, filling up around a half- or quarter-tank is good practice, especially during winter, 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.

It’s also good for the longevity of your car to keep it fueled up.

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.

Woodland of AAA said there are a few concrete ⁠ways to conserve fuel that don’t involve myths and urban legends.

Combining errands, paying cash and avoiding aggressive acceleration are all proven ways to make gas last longer, Woodland said.

This article originally appeared on Detroit Free Press

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