It's no just speed, run at as high of gear as you can, hence as low of rpm, shift points should be about 1500 unless your pulling a hill. On a grade don't be afraid of doing your road speed a little.Stay in a great that your truck easily pulls the hill without running hot, if your engine temp is above 200 degrees door down and drop as gear, leave your hair off except when going down a hill, engine brakes are for maintaining speed not reducing speed. Red lights, slow before you get there the game is not to stop keep it rolling saves you fuel. Kill your ac when climbing hills. Saving fuel it's a frame of mind not just one thing, it's all of it working together. Fuel in the mornings, the fuel is denser when cool, means you actually get more fuel than when it's hot. Cut your idle time, don't idle sitting in line, such as waiting to fuel.anytime your going to be sitting more than a few minutes kill the engine, with these new engines there is no reason to idle. Hope this helps. I drive a kw Cummings red top, pull a 53' refer, 79+ on every load. Jbswift pork west, with Ramona's burritos east. 13 speed trans. I run 80,15,58,99 so it is not all flat. Still average 8+ in ca because of the low speed limit, out of ca, in nv, ut, wy, ne,is running 75 I still average 6.5 to 7.0. Speed is the only difference between 6.5 and 8. If it was my truck I would run 55 to 60, but since I don't pay the fuel and the company doesn't seem to care,I dial it up.
Fuel mileage stories are a lot like fish stories. You can't tell for sure, but you can smell for sure. Like I tell my kids, if it's brown, sticks to the side of your shoe, and smells real bad, it's dog #@$&. Heavy means less mpg, lighter means easier mpg, hills, stop and go, you don't control. You do control tire inflation (a great resource for increasing mpg) idling is the enemy of mph, and diving into stops, pushing your tach on acceleration, generally flogging your rig lowers mpg. Drive soft, run those tires 100psi cold (more on trailer tires) and it averages out. You have run that thread on cummins tuning? You have to start with your rig running good, that's a given.
5 pages of replies and nobody has asked what route he takes and what speed he's driving? Or did I miss it? I do similar weights with double drops and I've been getting 6.0-6.3 lately. Hope to push 7.0 when the summer blends arrive. I have some hills to deal with on I-81 from Watertown to Harrisburg. 1998 T800, M11 Cummins, 13 OD, 4.33 rear, el cheapo low pro closed shoulder lugs on 22.5 rims, 60-62 mph target...58 mph average
