Tarnished/brown rocker arms/head
 

Greetings All,

This may sound like a dumb question but I'm asking it anyway. I own a diesel engined Benz as well as a gas driven one and when I adjust the diesel valve gap and pull the valve cover the valve train assembly looks extremely clean with no tarnish or browned or what I call burt oil stains on any of the assemblies on the diesel. When I change oil on the 6 cyl. gas engine the valve train looks brown and tarnished when I pull the oil filler cap and look inside. What's the deal? Has the previous owner run the oil too long in this engine or is this normal for an engine with over 170,000 on it? Is there a way to clean the valve train assembly using a different oil or switching to a synthetic or some additive? I'd just like a clean looking and running engine internally as well on this gas burner. Any suggestions on how to clean an engine from the inside out would be greatly appreciated.

Thanks,

Charles