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I own a 2003,2500 HD crew cab, 8.1 5 speed auto, 3.73 gears, with long box (34 gallon tank), less than a year. I have over 27,000 miles on it and just love driving the truck. Empty:
The best I ever get is 17 mpg on freeway at 65mph long trips. Driving Hiway 101 on the west coast, I get about 14.5. Running around town I'm lucky to get 10 mpg. Best fuel economy is acheived on long trips. Where you shut the engine off just long enough to fill it up. A week of short runs, 8 to 10 miles at a time will scare you at the gas pump. Towing:
Just came back from vacation in Death Vally towing a 26E Mallard(16,000CGVW). Mileage ranged from 8 to 10.5. Getting 10.5 requires a lot of effort to conserve and good road. I get 8.5 to 9 mpg with over drive locked out and cruise set at 65. Best fuel mileage acheived in overdrive, under 60 mph. I really dont think a diesel stands a chance of keeping up with or out running the 8.1, up a 6% to 9% hill or any hill! The "torque/RPM range of the gas engine allows you be at least one gear lower then the diesel. Gas engine 4500 rpm 2nd gear 60 mph. The Diesel has to shift to 4th gear to reach 60mhp @ 2500rpm. The diesel is turning 3200 rpm at 55mph in third gear. Assuming vehicles using 3.73 final drive and 5 spd Allison transmission. I think wide open throttle shifts are just below 5,000 rpm for the 8.1. I have a freind that has a 6.0 with 4:10 gears that I tow with. When he gets about 7 to 8 MPG towing, I get over 9 mpg. You may find this link interesting
Link From reading the article, I beleive my 8.1 is running slightly stronger. Than the vehicle they tested. More than my 2 cents, sorry.. Emery
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