This link was posted over on the Camaro Forum, and some of you may have already seen it. For those who haven't, it may give you something new to chew on.

The link shows the results of using LUCAS OIL treatment, and its likely that STP, EOS or other similar oil additives could do the same thing. The link shows gears, not an engine, but its not much of a stretch to think that an engine could see similar results, considering that the typical spur gear oil pump is, well, a couple of gears just like in the link pictures. Its like oil companies and car manufacturers say, never use oil additives. This link shows a good reason why.

For what its worth, some years ago I bought a brand new pickup, and after some initial break-in, I added a bottle of STP, to make sure the engine would last seemingly forever. Wrong, it developed a rod knock, not long after. Then the engine had to be torn down with only about 2,000 miles on it to get the rod bearings replaced, under warranty :-) My experience seems to be consistent with what we see here, and using STP was the only thing that was out of the ordinary. All those air bubbles mean less oil where you need it. I never used addivitives again, and never had any problems again. Some people do use additives without issue, but you could be taking a big chance with your engine. Something to think about the next time you consider using an additive again or for the first time. If you use the right oil, you won't need any additives anyway.

http://www.bobistheoilguy.com/images/lucas/lucas.htm