Peak Torque of 1050 ft-lb is reached at 1400 RPM, it would be recommend for
best overall performance and fuel mileage, to run the engine at approx.
On my next trip at the end of this month I will try running at 1700 rpm to see if I get better fuel mileage. I can maintain these rpm at lower speeds by locking out 6th gear if needed. I also realize that tire pressure, breaking and terrain come into play here. Thanks for the info that you guys provided. It got me curious. I'll let you know if I improved my fuel mileage.
Read VERY carefully the statement they give you. They did NOT, repeat NOT address what RPM to run the engine for best MPG. They gave an almost double talk answer of BEST OVERALL PERFORMANCE and fuel mileage.
You will get better MPG at closer to 1500 RPM if on relatively flat terrain (where it does not downshift on every upgrade). In rolling hills/mountains, you will need to run a little faster to get closer to "Best Overall Performance."
1500 and "economy mode" on the Allison will likely give you best MPG.