If the gum deposit is not very severe, add approximately 5% of acetone to the gasoline, which is in the tank. The gasoline-acetone mixture should be left in the tank for about 24 hours, and when burned by running the engine, it will tend to clean the carburetor and other parts of the fuel system.

If there is a lot of gum present, enough acetone should be poured into the tank to cover completely and allowed to stand for an hour. If the solution can be agitated so much the better. Very heavy gum deposits may require that the operation be repeated. Once the tank appears clean, it is desirable to add 1% to 2% of acetone to the first tankful of fresh gasoline. When burned with the fuel, the acetone will help eliminate sticky valves as well as help clean the fuel system of any remaining gum.

If acetone is not available, alcohol may be used, but more will be needed, and it will work more slowly.

   June 1949 - Antique Automobile