Marvel Mystery Oil is an additive that was fist sold in 1923 through the Marvel Oil Company. It was created to clean the carburetors in engines made after World War I, as they would easily get clogged. The gasoline at that time was low-grade and would often coat the carburetors with lead deposits or other contaminants. In addition to cleaning, Marvel Mystery Oil also increases gas mileage, decreases engine wear and improves overall performance. It can be safely added to automatic transmissions to clean deposits and reduce wear.
Pour the amount of Marvel Mystery Oil you are going to use into the measuring cup. Up to 16 ounces may be added to an automatic transmission. In smaller cars, 10 to 12 ounces should be enough.
Drain the same amount of transmission fluid into the pan. For example, if you are going to add 16 ounces of Marvel Mystery Oil, drain 16 ounces of transmission fluid. Refer to your owner's manual if you not sure where the drain plug is.
Open the hood and remove the cap from the transmission fluid cylinder. Place the funnel into the hole.
Pour the Marvel Mystery Oil into the transmission. Replace the cap, making sure it is on securely, and close the hood.
Start your car and run your engine for 20 minutes or so. This will warm up the transmission fluid and give an accurate reading when you measure it with a dipstick.
Let the car cool down for a couple of minutes. Open your car hood and remove the dipstick from the transmission. If you are not sure where it is, refer to your owners manual. Make sure it is not the oil dipstick.
Wipe the dipstick clean with a rag and then re-insert it. Pull it out again, and check if the amount of fluid reaches the "full" level marker. If for some reason it is low, refill the transmission with some of the drained transmission fluid. Make sure not to overfill it. Repeat this process until it is full.
Put the dipstick back into place and close the hood.
