The average amount of transmission fluid a passenger car can hold is approximately 12 quarts, but it can be as much as 36 quarts dependent on the vehicle model and type. The owner's manual for a vehicle lists the amount of transmission fluid that the vehicle's engine can hold.
Different transmission types use different fluids. Automatic transmission fluid is used for automatic transmissions, whereas manual transmissions use regular motor oil, heavyweight hypoid gear oil or automatic transmission fluid. The fluid type required is also provided in the owner's manual. Popular Mechanics recommends changing the transmission fluid on a regular basis to avoid the need for major repairs.