Yes, thanks slipstream444 for the advice of doing it a tankful or so before an oil change. In fact that is what I do, but forgot to mention it. If you go to some of those jiffy lube places, they try to talk you into adding the Techron at your oil change... not good, then any blowby will be in your oil for the whole duration. Also thanks for the note of caution to indymac. I hope doing it at the end of the oil change interval minimizes this potential problem.