I was talking to a friend of mine who drag races and we got off on a tangent about oil. He highly recommended that I should use Rotella 15W-40 in my 91 Supra Marauder with the PCM454 or go get a packet of GM assembly lube and add 2oz at each oil change. The previous owner had always used Penzoil 40w. My friend said the issue is the older motors don't have roller cams and need the metal additives in Rotella or most other "off road" or diesel engine oils. He said a few years ago most of these additives were removed or reduced in all the "on road" engine oils because it caused issues in the catalytic converters. The newer engines didn't need the additives because they were mostly roller cams. He said not running the Rotella, adding the assembly lube, or running a racing oil will greatly increase the risk of wiping the cam shaft in these older motors.
Seems sensible to me. Anyone else heard this concern?