Is there a break in period on the 6.7 truck? Someone told me I couldn't tow for 1500 miles. I scratched my head on that one. Also when is first service?

 

Read your manual, it explains everything. 500 miles before towing.

 

I dunno but I got an extra 5 mph on a large grade in our area called parleys canyon, I was pulling the same trailer and last fall when the truck was new I got 75 mph at the top and the other day I did 80 over the top. don't know if winter fuel was a factor, truck has 12k miles on it now.

another thing I found was that the truck runs alittle harder with your foot a bit off the floor, it seems to slow a little if you push the pedal all the way to the floor. running 3/4 throttle seems to be the way to get the most from it.

 

500 miles before towing (to allow the ring and pinion to wear in) and 1000 miles engine break-in.

 

Attached is a document that should get you started.
The manual explains quite a bit.