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How to Clean Out Varnish in a Gas Tank


If you don’t drive a vehicle and you let gas sit in a tank for awhile, it will become old. Old gas looks dark and smells sour. After a couple months or so, the gas will evaporate and leave a varnish residue in the tank. Varnish is a sticky, caramel-color substance. It will gum up the fuel system in a vehicle. You can easily clean the varnish out of a gas tank with a few materials and some time.

Step 1

Remove the gas tank from the vehicle (see resources). Basically, you’ll need to jack the vehicle up and remove the straps that hold it in place. Put the tank in a well-ventilated area away from sparks and flames.

Step 2

Use a siphon to empty out any gas that may be in the tank. Spray the inside of the tank out thoroughly with a garden hose. Dump out the water.