Great info Jeff. If I can find CJ-4 Delvac, Delo or Rotella, that's what I'll buy for my PSD. I have no 'Big Oil' brand loyalty whatsoever when it comes to lubrication. Though I'm still amazed that Delvac syn is so darn difficult to find in gallon jugs except online! If I can only convince my Wife that I need a 55 gallon drum of the stuff....