Lower oil pressure.

[jared43758]

Any one else make a switch to 5/40 t6 oil and notice a drop in oil pressure. Not at highway speed. About 46. But at idle it went from 38 to 31 now. Engine warm

 

[AKDoug]

Considering that the reports are that the oil pressure reading on our trucks is an algorithm and not a real readout, I don't know if it matters. Cummins uses high volume and lower pressure on their engines. I have over a million miles on two ISX Cummins motors. They run about half the oil pressure my Cat motors do. I consider 30 PSI at idle to be normal.

 

[Burn'n Oil]

Changed to the T6 Rotella back in Oct. Cold oil pressures were higher than with the factory fill - hot oil pressures were consistent with the factory fill. And then there's the can-o-worms that this subj can get ya into. Apparently (anecdotally), these vehicles do no employ an oil pressure transmitter per se but rather, an oil pressure switch. Therefore, the oil pressure indication the customer observes is a calculated/processed value that is based on engine temperature, oil temperature, OAT etc etc. It's frequently referred to as "fake oil pressure." With that in mind, I have no idea how the PCM figures out that the customer poured three gals of oil into the engine with a different viscosity. Or maybe there actually is an oil pressure transmitter hiding in there somewhere. Dunno... However, if someone out there does know (empirically, plse - not interwebs lore), then plse, chime in!

Fer sh_ts & giggles... The Diesel Supplement to the OM says 10 PSI min for idle and 30 for highway/loaded ops. Apparently not related to oil viscosity.