WOW, I can spot all the Dodge/Cummins owners! In ideal conditions, I would set my cruise control to 63 MPH, right around 1,800 RPM. Sometimes, you have to go a little faster, to pass etc. At those speeds I feel for the most part I am keeping up with the flow of traffic. Going to slow causes more problems than speeding! If your doing 55 in a 70 MPH zone, and most people are doing 75, you are going 20 MPH slower than everyone else, people get frustrated and change lanes, take chances just to get around you, that usually causes problems, not for you but for the other guy. Just cause you are not in a rush, does not mean someone else is! If you insist on going that slow, then get off the Interstate, use the secondary roads!