Oil changes often?

Any noticeable drop in mpg's? Down on power? Have injector cups ever been replaced?

 

Is your truck a DEF vehicle with the DEF system deleted? That causes all sorts of wonky issues for some trucks.

 

Company changes the oil on all our trucks between 17K and 22K, all we haul is intermodal, zero issues. Macks and KW's, sounds like you've got other issues

 

If an oil change fixes it then I think maybe your oil is getting diluted by fuel. I’d get an oil analysis.

 

Also, I know we do oil sampling/analysis at least once or twice per year.

 

I think that's your answer right there. You are gonna waste more money on oil and filters that if you had just maintained your DEF/DPF system.

 

I had a number of trucks like this, I got rid of a few of them but the two I kept I sent over to the Cummins shop and they pulled the pan and bearings, the thrust surfaces on the bearing were worn down. The fresh oil acted as a seal of sorts as explained by the head mechanic, when the truck was under a heavy load the crank would ride the thrust surface hard and cause the oil seal to disappear, when it was on a a lighter load, the oil pressure was a lot lower until the next oil change.