It should also be noted that many manufacturers have released statements and recommendations that people DO NOT do this on their engines. A reason why is when the chemical gets put in your oil its being mixed throughout the whole engine even though its "cleaning" alot of those deposit get stuck in places like the valve springs and cause catastrophic failure. I would never had anything to my oil thats just me, I use synthetics to keep my engine healthy and free of buildup. Just my opinion as my Dad is in the car business and has had numerous people come in with bad motors who have just done some type of internal cleaning..