Every now and again, I get this thought running through my head, wondering if I am using the best oil possible in my vehicles. I guess this is often in relation to the C5Z, since the journal bearings in the twin turbos are probably more prone to premature failure if the lubricating oil isn't up to snuff for those very high speed spinning turbines.
Anyway, I always tend to come back to this publication I found a while back ->
https://540ratblog.wordpress.com/201...-test-ranking/
Not sure how uptodate it is, but I tend to use it often and give it a lot of credence, whether it is actually due or not.
As such, most recently I have gone to the 5W30 Amsoil Signature Series, synthetic oil for the C5Z. Seems to be highly regarded by most people.
If I can find a reliable and consistent source of it, at a reasonable price, I may very well use it for all of the vehicles. The only immediately noticeable 2 flies in that ointment is that the hemi engine in the Jeep Grand Cherokee specifies that 20 weight oil MUST be used. Something to do with the valving for the MDS (Multi Displacement System). And it does not have the Chrysler recommended API certification label on the bottle. But for the latter concern, I can't see where using a top of the line quality oil would ever be a cause for any sort of lubrication based failure in an engine. As for the MDS, heck, I would just as soon have all eight cylinders running full time any way. I didn't buy the Trailhawk with the hemi engine with fuel conservation at the top of the list of concerns.