1st post - so hello everyone.
As the speed conversation goes, I just returned from a 900 i95 trip and did a test on speed / mileage.
On my 07 ISL Cummins I used 72-73 on the way and 67-68 on the trip back. Cruise control any time possible, same route. Low amount of traffic either way. Mileage went from 6.4 to 7.1. Just my 2 cents.
Mike