I have a friend that has a small shop that does auto repairs and he buys 1 qt. containers of oil by the cases to do oil changes on customers cars he uses 5w20 5w30 and 10w30 either cam 2 or conoco and after he uses the quarts he drains the remaining drops into a big container and uses that in his own cars. He mixes everything together and his cars run great. This guy wastes nothing and keeps his shop cleaner than most people keep their houses. Total neat freak my shop is the other way not so neat and clean