All of the things discussed lose lubricity and you end up with metal against metal. I thought everyone knew about Auto-RX, the non harmful chemical cleaner. I have used it on two different engines with amazing results. The product is at Auto-Rx Non-Toxic Sludge Remover and Cleaner for Engines and Transmissions
Good luck,
Anziani
'97 CL500 135K
'95 E420 129K