New FREIGHTLINER design, for all you Truckers...

Best I recall seeing was mid-7's. Truck was a FL Columbia, I think a DD60 (might have been a Cummins), with a 13-speed. He had set the truck up for mileage: overdrive trans, wheel discs on tractor and trailer, smooth-side trailer, and even ran rib tires on the drives. Also little things like low-drag mirrors, no fender mirrors, gap between trailer & sleeper as small as possible, trailer skirts, etc.

Is your truck a DPF truck?