just wanted to ask the very same thing....lemme paste here what I read sa kotse.com:

"Ingat mga Tol!!! Friends from car casas told me that most of the cars being brought in for overhaul are those using oil additives or protective coatings. It alters the micro-distances between moving parts...so parang sumisikip. imagine what would that product do inside your engine. sa halip na may micro-mm na allowance between parts to allow "play", sisikip siya because of the additional coating and all the pressures of moving parts will be absorbed by the parts itself, so nagse-self destruct ang engine parts mo. ask your friends in casas before you try any product for your engine. it might even void the warranty of the manufacturer kung pre-mature na nag-breakdown engine mo. buti na yung sigurado. pls consult your mechanics first"

if you will read the article sa XADO website, parang napakagaling....kulang na 10k lang...para ka nang nakapagpa-overhaul!

your expert opinions please....