[Adger Smith]

Alan has hit the nail on the head.
There is also another issue with some additives: oil filter.
Is it compatible with the enzimes that hold the paper in your oil filter together or does the paper filter it all out?
Quite a few years ago, As a Dodge diesel owner, I got a warning about using Fram filters. Seems the enzimes in the filter didn't like the diesel fuel mixed with the oil and the paper would come apart and stop up the jets that spray oil in the piston/cyl wall.
Sometimes my customers ask me if I like XXXX added to the oil. When I have no experience with XXXX I ask them if they have ever mixed it with the oil they use and see if it settles out or will stay mixed. Or I ask: is that the stuff I found sticking to the bottom of your oil pan? I always suggest pouring any additive into a partial bottle of oil and mixing before adding it to the engine.
I sell a bottle of Comp with each FT engine and suggest it be mixed with a partial qt. of oil and added just before starting the engine.