How to prevent frozen fuel lines this winter

Ron asks by email:

I was at a few places on Saturday and heard a customer asking the workers, where they could find anything to add to the gas so it would help prevent it from freezing. Apparently, someone told them that if they don’t add stuff to the gas tank, the gas could freeze. I tried to explain to them that as long the car had at least 1/4 tank, then the gas line will not freeze.

I left the store and outside I heard two people disagreeing about what the octane gas they were going to use to fill their tanks. One was saying they were told that in the winter it is best to use the higher octane and not use what they normally use. The other person was saying to just fill the tank with BP gas because they put antifreeze stuff in their tanks. What are your recommendations?


Cold weather does create many questions as to what is the best thing to do to prevent problems. Ron, you are correct that it is considered to be the best practice to always keep the fuel tank above a quarter. For all practical purposes, it is the water in the fuel line that freezes in cold weather and not the gasoline itself. When the gas level drops, the rest of the tank contains air. Then when the temperature drops, any moisture in the air condenses and drips into the fuel tank. Water is heavier than gasoline so it sinks to the bottom. Keeping the fuel tank level above a quarter helps keep moisture out of the tank.

Another reason that gas line freeze-up seldom occurs lately is that gasoline contains up to ten percent alcohol (ethanol). Alcohol absorbs any water that gets into the fuel tank. Regarding what octane gas to use, the short answer is to use whatever the vehicle specifies to use, which is usually regular grade. All gasoline, regardless of the brand, is blended for each season so in the cold weather months, gasoline is blended to allow the engine to start when the temperatures are low. That is one of the reasons to always use fresh fuel. Therefore, for best overall vehicle operation in cold weather, use the same octane as normal and keep the fuel tank as full as possible.

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