The Numbers Are In

[Greenleaf]

Upon returning from my week long trip to the south I configured the numbers for the truck. My signature will give my truck specs. Of special note, my truck has different sized tires than the factory calls for. Yah, my speedo is off 6MPH. I think these tires are smaller than factory. When the needle says 60MPH, I'm only going 54. Also my fuel gauge is WAY off. At a reading of 1/4 tank remaining I've only begun to use 15 gallons.



The only problem ; while driving in the Shiloh Battlefield Military Park, my speed sensor went south with out me. Picked one up in Nashville for $70 and everything was peaches & cream from there.



Look 'em over and compare to yours.



Total Miles; 1,909

Total Gallons Diesel; 83. 7

Average Cost/Gallon' $1. 42 High; 1. 69 in Memphis Low; 1. 32 Nashville

Average MPG; 22. 4 Highest; 24. 7 Lowest; 20. 5

Note, I have a heavy foot and ran A/C most all the time. Used the cruise only on the interstate highways. I drove near the speed limit, 73/75MPH.



Scott

 

[cerberusiam]

I have the exact same truck. Even on its best day bone stock and clean filters would it do over 21 mpg and it was a total dog. Thats pretty good mileage. If the truck is not a dog and pulls well then it is excellent.

 

[RMarx]

You guys are making me miss my '93 W250. I remember getting 20+ mpg but not any more. The new/improved '02 2500 is getting about 16mpg!

 

[Bluebird]

OD on or off?

Good mileage Greenleaf I have read here recently that some folks leave the OD off in around town driving. My mpg's are lower in neighborhood driving but, the truck does go into OD on longer streets when I'm going over 42mph. Would my overall average mpg's be better if I left the OD off until I get on the highway or freeway? Thanks for any input, Patrick.

 

[Greenleaf]

Overdrive is left in. I only turn[ed] it off when driving in the mountains. And often I must resort to 2nd. Helps me keep the speed down on the winding downward spirals. At home I never turn it off. My OD comes in at 35 indicated. Because of smaller tires, it's actually 29MPH. Doesn't bother me. Doesn't seem to be lugging it any. Some of my best mileage includes[ed] in city miles. I'm believing you would want to keep it on, but some don't like it shifting into OD while in the city.



Perhaps I'll keep this sized tire. I don't like the speed indicator off so . I'm guessing that with the proper size it should get me better MPG because the engine's RPM will drop.



I was surprised too at the figures. I had never before tracked it. My best figures came from city driving included with interstate and I was performing some jack-rabbit starts to boot.



Scott

 

[dpuckett]

In Mom's I keep the OD out until about 50 mph (3. 54). If you research Brake Specific Fuel Consumption numbers, along with TC ineffiency, you will do a little better keeping your RPMs up a bit. At the lowest BSFC (1700), out TCs arent very efficient. In my truck, (4. 11), I go into 5th at about 50.

Greenleaf, your speedo is a certain percentage off. Not a steady 6 mph throughout the scale. If at 60, you are really doing 54, you're 10% off. So at 35, you're doing 31. Not as far off. At least that has been my experience

Daniel

 

[boatpuller]

The main reason to keep your overdrive off until around 50 MPH is not because of lugging the mighty Cummins but because of the torque that it has at those lower RPMs, it will destroy your automatic. It is hard on your transmission to use overdrive at low speeds.



Just my $. 02



Caleb

 

[Greenleaf]

I have heard that. In doing so, this may[??]prevent some wear/tear on the OD clutch as it won't be shifting in/out repeatedly while in town.

 

[Bluebird]

Auto transmission shifts...

Thanks for all the info and tips... I guess I could dig out my owners manual but I'll ask here. With the OD off my truck does not shift into 3rd at 35mph like it does when the OD is on. Is this normal? Or, will it just go into 3rd at a faster mph

Patrick.

 

[boatpuller]

The overdrive switch will not affect the 2-3 shift only the 3-4 shift, 2-3 shift is controlled by the cable hooked to the throttle linkage and by the valve body in the transmission.



Hope this helps,

Caleb