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While it’s obviously impossible to keep your gas tank full at all times, it’s a good idea to fill up as often as you practically can in winter. And if you have an EV, keeping it charged (at least above 20 percent) is also strongly recommended for different reasons. A handful of cold-weather considerations factor in—here’s the rundown explaining why.
Benefits of Keeping a Car Fueled Up in Winter
Preventing Condensation and Fuel-Line Freeze
The main reason I try to keep all my cars topped off in the snowy season is to minimize condensation in the gas tank. The less fuel that’s in there, the more room there is for condensation to form inside the tank. Condensation means water. As temps fluctuate between warmer days and freezing nights, little teenie condensation droplets can become liquid water. If you’re very unlucky, water could make it all the way through the lines and into the engine, potentially causing real damage. It could certainly introduce rust from the inside-out, or even freeze and create blockages if it sits too long.
Protecting the Fuel Pump
This is largely an expansion of the condensation issue. Water is heavier than gasoline, and fuel pumps naturally pull from the bottom of the tank. So, if miniature icebergs form inside your fuel tank, they’ll sink to the bottom and potentially clog up your fuel pump.
But also, electric fuel pumps use the gasoline they’re surrounded by as a coolant and a lubricant. When your gas is low, the pump can be exposed to air, which could make it run hotter and wear out prematurely.
Building an Emergency Buffer
This point is less science-y and more practical. If you do get stuck somewhere, or your commute takes longer (likely!), it’s comforting to have more fuel in reserve. Worst case, if you’re bogged and waiting for a tow truck, a full tank means you can run the car longer and keep the heater on safely.
Added Weight Means Better Traction
This really only applies to trucks and rear-wheel-drive cars, but if you’re in one of those, this isn’t trivial. Gasoline weighs about six pounds per gallon; having a full tank puts more weight right over the drive wheels, which can be a helpful traction aid in the snow. You won’t have this benefit in a front-drive car, and it’s pretty much trivial in something like a modern super-heavy SUV. But in my old Bimmers, this can be a boon!
For EVs: Battery Preservation
Extreme cold slows the chemical reactions inside lithium-ion batteries, which means reduced range. It’s now pretty well-documented that EVs can’t go quite as far in winter as they can in summer because of this (and the fact that you’re more likely to be running high-draw heating accessories). But even if you’re not planning to go far, leaving an electric vehicle with a low state of charge overnight in the cold season can leave you with a bricked vehicle if the temperature drops suddenly. This becomes more of an issue the longer the car needs to sit. Keeping the battery charged above 20% in the winter is crucial.
Here’s a Tip if Your Car’s Already Been Sitting With Low Fuel in the Freezing Cold
Don’t panic. On the upside, most gasoline sold today is 10% ethanol. Ethanol is a type of alcohol; therefore, whatever fuel is in your tank already has some degree of water countermeasure. However, if it’s really been a while since the car’s run, and there have been freeze/thaw cycles where it’s parked, it might behoove you to throw in some fuel additive.
A product like ISO-HEET is cheap insurance against gas-tank water. Add some in before topping off your fuel tank for max effect (the turbulence of the gas rushing in helps mix it). Full disclosure, our parent company does get a commission if you buy something off our links. But I wouldn’t mention it if it weren’t legit. There are other brands too, all of which should be readily available at auto parts stores, hardware stores, and sometimes even gas stations. If you’re standing in an aisle looking at a million options for “water-from-fuel remover,” I say just grab the cheapest one that’s compatible with your car.
The bottles should clearly state how many gallons of gas they treat—and you can easily Google (or ask AI) how many gallons your car’s fuel tank holds.
Wait, Did You Say Your Car’s Been Sitting? Look Out for the Battery, Too
A cold start in freezing conditions puts a lot of strain on your car’s battery. How much that affects you depends on a few factors, which could be a whole other blog post, but I’ll run through it quickly here, too.
If your battery’s more than a couple of years old and the car’s been sitting in freezing conditions for three weeks or more, I seriously recommend bringing the battery inside and putting it on a slow charger instead of trying to jump-start it. NOCO makes a bunch at different price points—this $60 NOCO Genius 5 is a strong pick (another affiliate link, but also an earnest recommendation).
Once you do start the car, you really should drive it for at least 20 minutes to give the alternator the chance to revive the battery. This will also help burn off moisture that might have formed in the engine’s crankcase (once again, moisture kills cars, and internal moisture is the worst).
Good luck out there!
Automotive journalist since 2013, Andrew primarily coordinates features, sponsored content, and multi-departmental initiatives at The Drive.
