Yes, I am using Royal Purple 15W40 API Licensed CH-4 / SJ oil.
Been in the truck since 5K. With LF 3552 changed at average 4K intervals, I would change the oil once every 12K. It was still good at that point. Oil analysis was performed on average once per 12K just to provide a trend analysis.
At 110K, I added an OilGuard Bypass filter (
www.oilguard.com).
I am now at 128K and plan on changing the oil at 25K along with the bypass filter. Been changing the LF 3552 every 6K.
I am going to try a Nelson EcoClean Filter in place of the LF3552 and will see if it is as good as the LF3552 or maybe better.
I know of other Cummins truck owners that are running 30K on Royal Purple 15W40 with bypass filters.
An alternative to the more expensive bypass kits available from various sources is to build one yourself from FleetGuard parts.
Use an LF777 filter ($15), use the remote filter head available from FleetGuard ($26), build a bracket to mount the assembly in an appropriate location (frame rail beside transmission or front cross member under radiator)
Plumb it with 3/8 Rubber Hydraulic Hose with push on fittings or Aeroquip line.
Pick up pressurized oil from the oil sending unit with a tee fitting. This line goes to the inlet of the filter head. The outlet line should return to an unpressurized location on the engine (valve cover or top of the crankcase). In the outlet of the filter head, there is a built in restriction (smaller outlet orifice) to limit the volume of oil flowing through the bypass filter. (This is about 5% total flow of the engine).
Total cost should be well under $100 depending whether you use Aeroquip and how fancy a braket is made. The replacement filters should be available at any truckstop or Fleetguard dealer and you can find alternatives in Baldwin, Wix, Luberfiner, Hastings, etc.