I was talking with a tech at the dealer that told me that it's best to run the cummins EGT between 600 and 800 degrees pre turbo and to get out of it ASAP if its over 800 but is capable of 1200 degrees in short bursts without problems. I have a heck of a time keeping it under 800 degrees while driving in the mountains empty. I know it will go way up with the trailer in tow. I believe these motors were made to work hard. I just don't see worrying about the temps so long as they don't go over 1200 degrees.