Hi... here is my update on the engine oil mashup: Bellringer RV Service in Waco, TX agreed that a mistake had been made and they drained the generator and engine oil and replaced with Delo Isosyn 15w-40 on their dime. All seems well now. I've done research on the Cummins 6.8.3 engine. It is perfectly normal for this engine to idle, when fully at operating temperature, at oil pressure as low as 5-10 pounds. At say 1600 RPM, under load, oil pressure will be about 55-65 pounds. Cummins informed me definitively that they do NOT recommend 5w-40 oil for their engines, or Onan/Cummins generators. After the second oil change, I'm getting about 17 pounds pressure at idle, at operating temperature (185 degrees F). So all seems OK now. BTW, I've learned that the 6.8.3 Cummins is a low oil pressure engine. Apparently, the oil pump is designed to only pump at low pressure. Some owners report that when warmed up, they get only 5lbs or less pressure. This is a known issue with this engine but they run and run and run for many many thousands of miles.
Elbridge Price, 1998 Dutch Star Diesel Pusher
Cummins 6.8.3 mechanical injectors, Spartan Chassis
2016 Toyota Prius; Acme EZE Tow Dolly