Originally Posted by Jerry Bransford
To me, all the hoopla about adding extra zinc is totally unecessary with a stock 4.0L engine. I'd only worry about today's reduced zinc levels on a built high-performance engine with higher than typical cam pressures from extra-stiff valve springs.
I happily run conventional 10W-30 Valvoline oil with no worries.
I am in the process of installing a new cam, lifters, push rods and rockers on my 2004 4.0 with 140,000 miles.
Theses motors were designed when motor oils contained zddp ( zinc / phosphorus, etc. ).
I went to a very well known and respected performance machine shop locally to purchase some "break-in" oil / Lubes.
The old timer pointed to several 4.0's that he was in the process of rebuilding. I saw with my own eyes worn cams and lifters just like mine. His very frank experienced assessment was that many "modern" oils were deficient in ZDDP due to federal mandates to protect catalytic converters.
He recommended Brad Penn oil. It has a higher level of ZDDP. Brad Penn oil was previously Kendall Oil. From 100% American Pennsylvania base stock. It is a VERY high grade quality motor oil. It is formulated for various applications. I will use the conventional 10-30 version.
So many of you can "happily" use whatever motor oil you want. If you're running a 4.0, then you can "happily" do this until you suffer lifter / cam failure.
Speaking from experience here.