OldWolf,

When I rant about the Rotella T 5W40 Synthetic in the Diesel there is a DisClaimer:
1.I treat the 5W40 just like it's a Mineral based Lube...3000 Miles and the Oil+ Filter gets changed.
[It's advantage is slightly lower cost and much more of a
Diesel additive package (CAN YOU SAY Zinc?) ]
2.As pointed out earlier,the OIL is the Coolant AND Lubricant for both the
Injection Pump AND the Turbocharger![AND Turbos BEAT the FOOL out of OIL]

DO NOT MIX: BRANDS , VISCOSITY(s) !
Nothing Good can come from "Playing" Petro-Chemist!

The Mobil 1 Truck and Turbodiesel [A.K.A. Delvac 1]is rated for C [Compression]type engines.

I would feel comfortable running 5K oil+ filter intervals with:
Royal Purple,Redline and Delvac 1 WITHOUT oil testing. (O.K. Amsoil Too)

__________________
'84 300SD sold
124.128