All comments considered, I can’t think of anywhere that I could drive, no faster than 50mph, and not get run over. cummins needs no “break in” other than to drive like you stole it. I towed right around the 500 mark. Left dealer, hopped on interstate, and 75-80 all the way home…..couple hundred miles or so. Do whatever you can get away with. No way to prove improper time of breaking, in my opinion, which is worth exactly $.001 due to inflation.