23 MPG Highway towin' trailer

[wildbill_hickup]

Just wanted to post this FYI. Probably most of you that own a truck like this(94 Dodge 12v Cummins, 4X4, 5 speed stock) aren't surprized, but I was, and pleasently I might add.

Just finished up a 600 mile trip, most was highway driving and the calculated amount was towin' a small/medium sized trailer pretty well loaded(Have no idea of the wieght). Here's the results, 596 miles, 26 gallons = 22.92MPG . Not bad in my book, a few pretty steep grades, never knocked it out of OD, came close once on a long climb, but it pulled it. Couldn't be happier. Hell I've got a S10 Blazer 4.3L V6 that barely gets 24 on the same trip no trailer. I have always gotten a kick out of these economy fuel efficient car adds boasting 'over 30 MPG' (now even more-so) that was being done 30 years ago, after this many years you would think they would be embarrased to advertize that, now 60 or 70 or 80 would be something to boast about. Anyway no rants, just gotta love that 12v

 

[stacerbob]

I know what you mean, guys will come in the shop with their econo car saying I get 35+ MPG in my sardine can, I say Oh thats pretty good, I just get 22 with my 7000# 4wd crew cab dually!!!

 

[argve]

yep yep... not uncommon at all

 

[Dadbrun]

How are you guys getting that good a mileage.My 97 with auto gets about 16 around town and the best it ever got on the highway was when it was new and it got 21.This is with no load.When I used to tow a 9000 lb excavator it dropped to about 10-12 combined loaded and empty around town. I am hoping this new injection pump and having the valves adjusted will help my mileage a little.

 

[ndurbin]

How are you guys getting that good a mileage.My 97 with auto gets about 16 around town and the best it ever got on the highway was when it was new and it got 21.This is with no load.When I used to tow a 9000 lb excavator it dropped to about 10-12 combined loaded and empty around town. I am hoping this new injection pump and having the valves adjusted will help my mileage a little.

Thats all the more my 94 gets usually. Autos are at a little disadvantage in the mileage department vs. manual trucks.

I get 17 usually on the highway (cruising @ 75), 15 around town, and 8-12 towing. Tho my towing mileage can vary greatly depending on what I am towing, how heavy it is, and distance I'm going.

 

[argve]

Yep the manual tranny makes a big difference in mileage because we aren't loosing any power coupling where as an auto does.

 

[ndurbin]

Tho getting 23 MPG while towing ya gotta have a very small lightweight trailer or it's really arrowdynamic. You hook onto a 5th wheel RV, a loaded flatbed goosneck, or a stock trailer (what I consider a trailer, anything under 16' is really an extension of the pick up bed IMO) and that 23 MPG will be a mirage wether it's a manual or auto.

 

[Swamp Donkey]

23 mpg! Wow. I have never ever got over 18 mpg empty with my 98 12v. That was even when I bought it new before any modifications. Some people have all the luck.

 

[wildbill_hickup]

OK,
It may not be as good as I thought. Yesterday I was working in an area where the local law had set up one of those speed boxes (you know that tell you how fast your going) I had to pass this thing several times durring the course of the day and I noticed that my speedo is reading 3-4 MPH fast. This may explain the excessive mileage. A fast speedo will put more mileage on the odo than correct, right???

By the way can anyone tell me the correct (factory) sized tires for this truck? It's a RAM 2500 5.9L 5 Speed pretty standard model with Reese Hitch and Diamond Plow. Right now I have 245-75-16's on it. Could these be giving the incorrect speedo reading.

 

[ndurbin]

Thats the standard size tire for our rigs.

 

[Dadbrun]

Bigger tires will make the odometer read less miles than what you are actually covering.For each round of the driveshaft or tranny it records x amount of those revolutions per mile,with bigger tires the driveshaft is turning the same revolutions but because of the larger circumference of the tire you are going farther per revolution.The offsetting side of that is that it takes more fuel to turn those larger tires.I have 285-16's on mine and I always read real close to the radar boxes that they set up.When the truck was knew it always read slower than the radar boxes.The circumference difference between 245 and 265 is pretty small but it does make a difference over that many revolutions.

 

[Dadbrun]

Bigger tires will make the odometer read less miles than what you are actually covering.For each round of the driveshaft or tranny it records x amount of those revolutions per mile,with bigger tires the driveshaft is turning the same revolutions but because of the larger circumference of the tire you are going farther per revolution.The offsetting side of that is that it takes more fuel to turn those larger tires.I have 285-16's on mine and I always read real close to the radar boxes that they set up.When the truck was knew it always read slower than the radar boxes.The circumference difference between 245 and 265 is pretty small but it does make a difference over that many revolutions.

 

[MMeier]

Thats the standard size tire for our rigs.

I thought 265's were stock size on a '94. Look at the sticker on the door jamb and see what it says. Which case, 245's would read more cause they "lower" your gear ratio a bit. My .02

 

[ndurbin]

I thought 265's were stock size on a '94. Look at the sticker on the door jamb and see what it says. Which case, 245's would read more cause they "lower" your gear ratio a bit. My .02

245 is the stock size for a 94.

Unless you got a dually then it's 235.

 

[MMeier]

245 is the stock size for a 94.

Unless you got a dually then it's 235.

Now I know 235's is wrong, duallys came with 215's... I know I had one !! And I'll go look for a SRW , still say 265 there.