Aaron Widmar
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Fact or Myth: Can Your Car’s Gasoline Freeze if Its Level Is Low?

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How cold temperatures affect your vehicle's gas tank

man pouring anti engine can gasoline freeze cold winter chill temperatures car vehicle

Winter does many terrible things to your car, straining its operation amid freezing temperatures and slowly rusting away its body. One of the most common winter car care tips we’ve heard is to make sure your vehicle’s gasoline tank is never below the halfway fill level — the reason being, if there’s not enough gasoline in the gas tank, it will freeze.

But is it true that gasoline can freeze if there’s not enough of it? Or is that just a myth propagated by the petroleum industry so we return to the pump more frequently?

Can Gasoline Freeze? How Cold Temperatures Affect Fuel

You wouldn’t think that gasoline would freeze, particularly when it’s in your car, but that’s probably what you’ve heard.

Well, gasoline freezes at -100ºF or below, depending on what exactly its mixture of liquid components is (octane freezes earlier than that). So unless you intend on driving in conditions that are that cold — and if you are, your car will experience more problems operating than just the gasoline freezing — you rarely will have your car cease functioning for that specific reason. Diesel, on the other hand, has a higher freezing point and could run into freezing problems, which is why winter diesel blends are sold.

But just because gasoline won’t freeze in your car doesn’t mean a low gas tank won’t be harmed by cold temperatures. If you repeatedly leave your gas tank at 1/4-tank or under, you may encounter one of these problems:

  • The gasoline may break down and its components could separate, with the heavier molecules collecting together (typically the paraffin wax content in an event called “gelled fuel”).
  • Any condensation or water vapor in the tank or line could freeze, which would hurt your car and inhibit its ability to function. Alcohol in gasoline absorbs water, but if there isn’t enough alcohol, not all the moisture will be absorbed.
  • Keeping the tank filled below half-full could shorten the life of the fuel pump.
  • You might have less fuel than your meter shows, especially once it cools, which could strand you somewhere with an empty tank.

However, most of these scenarios are unlikely, as ethanol-based gas and better fuel injection systems have improved over the past 30 years. If you are having problems with your gas line freezing, you’ll want to make sure there are no leaks in the line letting moisture into it. You can also use a gas line anti-freeze additive occasionally to wash out any water build-up.

Sources: University of Illinois at Urbana-Champaign Department of Physics, Do It Yourself

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