Here is something i heard years ago and again yesterday. Some people say that penzoil gets gritty and builds up deposits in an engine. A friend of mine took his toyota truck in for a complete tune up which included a valve lash adjustment. (the year was 1988) After the service the mechanic asked if my buddy used penz in his truck because there was lots of varnish, gritty material and a sticky film on the head and under the valve cover. The machanic said to use any oil other than penz to avoid problems in the future. By the way my friend did use penz. Yesterday i told a different friend to use penz instead of valvoline (courtesy of info from this site) because penz is a superior dino oil and he said no way penz gets gritty like sand and leaves heavy deposits of crap in your engine. So where did this folklore come from and is there any truth to it?