Reader Question: Dry Gas?

Here’s the latest reader question, along with my reply! 

Robert asks: What, exactly, is “dry” gas? And what does it do?

My reply: “Dry” gas isn’t gas – it’s actually a generic term for gas line anti-freeze sold under various brand names in small bottles that you pour into your car or truck’s fuel tank. These products usually contain about 70 percent isopropyl alcohol – the same thing as the rubbing alcohol you may have in your medicine cabinet.

So – why would you want to pour rubbing alcohol into your fuel tank? To get rid of any water that may have accumulated there as a result of condensation. It is not abnormal for there to be small amounts of water in your fuel tank all year – but during the winter, condensation and water-build-up becomes more of an issue. Accumulated water can freeze up in your fuel lines, causing hard starting, rough-running and stalling. Since water is heavier than gasoline, it tends to pool at the bottom of your gas tank – which just happens to be where the fuel pump pick-up (or the pump itself) that draws gasoline to the engine is typically located – so it gets sucked right into the lines. If you own an older car with a carburetor instead of fuel injection, water in the gas can also pool in the carburetor’s fuel bowl – displacing the gasoline and making it hard (or even impossible) to start your car.

The isopropyl alcohol in “dry” gas works by absorbing the water (as much as 10 times its own volume), allowing it to be carried through the fuel system to be burned up along with the gas.

End of problem!

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