Cummins Diesel MPG in an M-725?

[Seth]

Hey everyone, part of my M-725 transformation is putting in a new Cummins diesel engine. Although I know from experience that MPG varies vehicle to vehicle and it isn't much of an exact science, I am curious as to what you have gotten out of your personal rigs.

[Kamikaze12volts]

cannot really tell about your M725 but in my M715 i have a 6bta with A618 which give me .70 of overdrive turning 42 inches tires with rockwell axles ( 6.72 of ratio ) and my average mpg is around 20. Going at 45 mph on highway with my M104A1 trailer ( 2800 pounds empty ) If ridding the 715 alone i get a better MPG .... around 23. But if trying to speed up to 68 mph; Garmin certified ( which is my MAX speed , stock spring at 2500 rpm ) the mpg go down to around 8 MPG

Mine is not stock, so with a better ratio it may even be more economical

Hope this will help you ....

[randyscycle]

The flat windshield and brick-like aerodynamics of any military vehicle lends itself to poor fuel mileage at anything above about 30 MPH, no matter the engine.

[syzygy]

The flat windshield and brick-like aerodynamics of any military vehicle lends itself to poor fuel mileage at anything above about 30 MPH, no matter the engine.

True, but even 42s and OD won't totally make up for the deep gears in his rockwells. With more typical gearing/tires you'll be able to make lower RPM ratings at the same speeds, helping you out with lower fuel consumption. Like you said though, the faster you push a brick through the air the more wind resistance you're gonna get and fuel mileage will keep dropping exponentially as you try and speed up...

[Burritoboi5]

With my 4bt, 39 in tires and ford 5 speed with overdrive, oh 4.10 gears too I get 22 on the highway cruisin at 60. About 18 around town

[camoman]