Confused??About fuel milageMe and the finance company have a 2001 Dodge 2500

[Cpat]

Me and the bank have a 2001 Dodge with the 5. 9 comapart diesel engine ,automatic transmission 3/54 gears 4x4 LWB 305/16 Pro Comp AT tires on 8 inch rims.

Pulling my 97 Jeep Wrangler on a 16 foot flat open car trailer I can pull out at 2200 rpm 75 mphTOPS

average 9 to 10 mpg. After a trip to the local Cummins shop ,where they checked everything with a computer including the lift pump? They report average mileage since I've had the truck [15000 miles]is 13 mpg!!Most of my driving is in South Florida on flat land at 65 to 70 mph. After reading the TDR messages seems like I have a fuel guzzler! Had I known the mileage I would kept my 93 Ford with a 351. Also they say my tires are the problem. The stock tires are 285/16 Michelin which are 1/2 inch smaller than the Pro Comps.

Is this normal or am I missreading the stories of 18 mpg up on similar trucks,The truck is empty with a Leer cab height topper. Any suggestions is appreciated!!!

 

[SS]

Cpat,



Welcome to the TDR. Sorry to hear about your bad experience so far - maybe somebody here can diagnose it for you. My previous truck was a similar set-up to yours (with stock 265 tires) and with 2 Jeeps on the trailer it was no problem doing 80 and getting 10-11 mpg. With your topper you should have a little better aerodynamics than mine with the tonneau cover unless you have a huge lift. I know some guys do get lucky and have incredible fuel economy, but yours does seem low. My current truck lifted with 36" tires, 6-speed, and 4. 10 gears gets 16-17 mpg all-around driving hard on winter fuel.

 

[hawkerpilot]

helllo cpat

don`t feel bad my 2001 =11. 6 mpg empty with winter fuel 12. 8 summer fuel. I belive retarted fuel timming is the cause. a timming box or a timming/ fueling box may help both of our trucks. my old 95 12 valve =17 city 23 hwy liked it so much i bought a new truck!! 12 valve motor worked great with 3. 54 gears the 24 valve likes to rev and is better suited for 4. 11 gears which in most cases my produce better mpg . Also the 24 valve motor may have a higher lift cam than the 12 valve motor which will shift the power curve making the 24 valve a little weaker at lower rpm but stronger at high rpms where 4. 11 gears come in to play in a stock 24 valve .

 

[VicR]

Not a completely valid comparison, but my 99 2wd 6 speed gets about 19 towing my 66 Plymouth Fury Ragtop (4000+ lbs) on a tow dolly at 68 MPH/ 2000 RPM. (Above that the dolly would wander). This was 1000 miles to Gt. Falls, MT. On the way back, running empty at 80 plus (2400 RPM), I got 1 MPG less. On a recent trip back from LA I did about 60-65 MPH for several hundred miles at night through deer country, and got 23 MPG. <p>



My conclusion after 35,000 miles with this truck is that mileage drops off exponentially over 2000 RPM. I plan to get quick check II from Cummins and verify this someday.



-Vic

 

[Little Bill]

I've got an '01 6 speed (with a few tweaks), but without the big tires. I run the devil out of it in the flatlands of coastal carolina and get a consistant 17-18 mpg at 65-70. Any reflash stickers on it?

 

[MikeR]

Well, yes your tires are the cause of lower mpg readings. You're diving faster and longer on the same amount of fuel, so bigger tires are making the speedo click off less miles compared to the gallons you're using... this shouldn't be news to anybody.



Abbot makes a speedo corrector box for the 98-02 trucks, or some guys have reported the dealer able to reprogram the pcm if you have the revolutions per mile # of your bigger tires.



-Mike

 

[KatDiesel]

Originally posted by Cpat

They report average mileage since I've had the truck [15000 miles]is 13 mpg!!Most of my driving is in South Florida on flat land at 65 to 70 mph. After reading the TDR messages seems like I have a fuel guzzler! Had I known the mileage I would kept my 93 Ford with a 351. Also they say my tires are the problem. The stock tires are 285/16 Michelin which are 1/2 inch smaller than the Pro Comps.

First off the stock tires were 265/75/16. You now have 305/??/16 which is a bigger tire. You will lose milage turning them. Also as Mike pointed out make sure you are adding in "extra" miles that you have traveled but the odometer is not showing. I have 285/75/16 and I get 14. 5 to 15. 0 mpg, but I have some fuel sucking upgrades and my foot is usually on the floorboard unless its snowing. I got 18mpg a while back when I held back and drove 70 to 75mph on the highway. . but thats no fun to stay that speed for several hours.