How to clean a bad fuel tank with Sea Foam [SOLVED] (2024)

Thanks for the question, Dan.

Yes, you can use a mixture of Sea Foam Motor Treatment (or High Mileage) and fresh fuel at a ratio of 50/50. That ratio will be plenty strong to clean. Pour the mixture in the tank, and let it sit for 24-48 hours. Make sure it’s filled above the “contamination line.” Periodically, move the fuel tank around to get the mixture of Sea Foam and gas moving. It is best if you can get a little heat inside the tank, so leave it outside as long as you can in direct sunlight if that’s an option. Sea Foam works better at higher temperatures. Dispose of the fuel/Sea Foam mix once finished.

If this is a large tank, add two cans of Sea Foam to a low tank of fuel (2-3 gallons), and drive it until almost empty before refueling.

If you have small engine and want to clean that up at the same time, here’s what I’d try:

Add a can of Sea Foam followed by a gallon of fresh fuel. Start and run the engine for 8 minutes to allow the Sea Foam concentration to draw through the carburetor circuits. Shut off the engine and let the engine sit over night or longer (2 to 3 days is better). After the long cleaning soak, add another gallon of fresh gas and run the engine for 5 to 8 minutes to heat up. Then take it for a short spin to create more upper engine heat and compression. Much of the Sea Foam will remain in the tank and continue to clean as you go. At that point the fuel system and fuel passageways should be very clean!

After that, run a cleaning dose of Sea Foam Motor Treatment to a low tank of fuel (full can in 2-3 gallons of fuel, or the equivalent ratio), and drive till almost empty before refilling. The high concentration will help clean out any varnish in the rest of the fuel system.