How long, generally, is a break-in period?

Well did it get better after some miles? Fuel economy get better?
Just took delivery and I'd say the exact same thing you did. It better get better and be like the older Cummins or time for something else

 

Let that Cummins drop down to about 1100 before down shifting. Yes some Cummins have to get some miles on them before they start performing. That is if your boss hasn’t neutered it.

 

No actually you are way out of your torque range your using HP not torque let that engine work down low. Hell my 565 with a 18 and 3.25 pulls great at 1100 to 1200 rpm got to let them work in the power band.

 

Yeah same here. Thanks for getting back. Seems downshift early and get up to 1650 to save face. No low end torque at all. What a disappointment. Mileage the same as old truck and now $45/week in DEF. Figured would get better mileage to cover the DEF

 

Weird, I let it lug on down and once it starts pulling it pulls good. These new engines will bog down then start pulling.
Nothing like the old engines. Have to be driven differently and no idling

 

Mine came alive at 50k. Buddy of mine said his opened up at 70k.