The reason is that they do loosen up the junk, which is good temporarily. Not
good for long term stuff. the other aspect is that modern oil is very
advanced and I believe in leaving it alone. The oil market is very
competitive, see the commercials. If there was a better oil out there they
would do it and sell it to you with all the hype. I have done extensive
research on the web and I feel now that all those engine additives are junk.
they are just snake oil in a can.

Putting massive detergents in your oil and making it a thinner weight does
make sense right before you change it, however. I have also had problems
disproving the idea of putting something in the gas. nothings better than
powered lead but the EPA doesn't like that anymore.

Thanks

Todd T
84 Westy
Washington DC