Dodge Cummins Diesel Forum - View Single Post - Best Oil To use and Additives
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post #10 of (permalink) Old 10-02-2019, 12:34 PM
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Eh. Seen enough issues with synthetic motor oils that I'm not keen on it. Tends to develop a varnish layer. I run plain-jane Mobil 1 (best additive package in the SN class) in everything gasoline. Leaves minor varnish deposits in area where oil flow is stagnant/non-existant. Last place I worked ran Duratec ES in a fleet of Cummins L-series CNG engines, this stuff developed a nasty varnish layer on any surface that wasn't an active contact area, including the pushrods and pushrod holes. Doing valve adjustments on them, you could peel strips of it out of the valve cover like beef jerky. Could have been something with that specific oil formulation, the composition of the crankcase gasses in those engines, or the interaction between the two, but I have no inclination to try it in a diesel engine I care about. FWIW, the few diesel engines we had there ran Vecton (synthetic blend) and never had issues with varnish. They also got about 1/10th of the hours on them that the gaseous engines did.

Anymore, the differences between conventional and synthetic base stocks don't really have an impact on the performance of the oil. However, the conventional vs synthetic debate will never reach a resolution no matter what data or anecdotal evidence is provided.

Regardless of one's stance on conventional vs synthetic, I would advise staying away from over-the-counter CK-4 oils as they don't have the anti-wear protection of the earlier CJ-4 and CI-4 oils no matter what claims the marketeers are spouting. I plan to run a ZDDP-boosted 15w-40 conventional in my new engine with dual LF9028s remotely mounted. Can't say the oil brand because I work for them, but if you make use of certain information under my avatar, I'm sure you can figure it out. I also ran this oil before I worked for them and would continue using it if the company and I were to part ways.

The ZDDP-boosted oils are generally described as racing oils because that's the broadest market for them, but they are also a perfect match for our old trucks without exhaust aftertreatment devices.

'95 2500 ECLB 4x4, 334k and paused due to epic transformation in progress.
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