Berryman B-12 Chemtool Fuel System Cleaner (part #0116) is extremely effective in the removal of gum, sludge, and other crankcase deposits. However, there is a caveat—if sludge or carbon build-up on worn oil rings has been helping to seal the crankcase, then applying B-12 Chemtool could actually cause the engine to begin smoking even if it didn’t before. This is a very uncommon occurrence, but please be aware of the possibility. If you would like to use B-12 as an engine flush, pour into your cold crankcase approximately 1½-2 oz of B-12 Chemtool per quart of oil capacity. For instance, if your vehicle holds 5 quarts of oil, then you should use 7½-10 oz. of B-12 Chemtool. After you’ve added it to your cold engine oil, start the car and run it at idle 10-15 minutes or until the oil is warm. Then change the spent oil and replace the oil filter.