After looking around and reading I think that Auto-RX and CD-2 Oil Detergent are very similar if not basically the same. CD-2 smells like a high-quality synethetic oil (esters?) and has the same color as oil, but a bit lighter weight maybe a 5-10w? also I have read that CD-2 will send all the junk to your oil filter and you can see it in there if you cut it open like you can w/ ARX. Being that it's more readily available and less expensive, I think I may try it on an engine that's in need of cleaning. I have used CD-2 in the past on a car w/ noisy lifters and it does work for that too.