All gasoline and propane powered engines : Add 8 ounces for a 4 to 6 quart/liter engine oil crankcase capacity every 15,000 miles (24,000 KM). Diesel engines : For the first 15,000 miles (24,000 KM) add 2 ounces per quart/liter of engine oil crankcase capacity.Thereafter, add only 1 ounce per quart/liter every 15,000 miles (24,000 KM).