switching to synthetic
I'd have to do some label reading myself. One sure way to tell is the gpIII is almost always cheaper, at least the Rotella and Castrol stuff is. XOM has recently been moving some of their stuff to a gpIII base, but INCREASING the prices (Mobil1 EP, for example), so the lines are getting blurred.
As far as "slipperiness" goes, that's a new one on me. I know the lower levels of zinc-derived additives found in the latest EPA-mandated API standards classifications are an issue. But I can't understand how more slippery would translate to less movement in terms of an abnormal wear pattern. :dontknow: