Engine/Transmission (1998.5 - 2002) Why is my fuel mileage so much lower than everyone else's?

[Chace TX]

I am now driving the 5th Dodge Cummins 3/4 ton. All these figures are empty, w/ mixed 70% hwy and 30% city driving. The first one was a 91 D250 2wd 5-speed, it got 20mpg on every tank, all the way to the day I sold it at 190K. The 95 auto 2wd got 17-20mpg while I had it. The 97 4x4 auto excab got 14-16mpg, I tried everything (timing adjustments, different plates, new overflow valve, fuel additives, etc), and it never got over 16mpg. The 01 2wd 5spd, got 17-20mpg, and now the 02 4x4 auto is getting 14. 6mpg on the last two tanks. I have read time and time again of people getting upwards of 20mpg with their 4x4 autos, and 21+ from the 2wd's. The new one has 26,000 miles so it should be broken in. On the last two tanks I am running an AFE megacannon, and a comp with the pump wire untapped. I put on 285/75R16's and adjusted the mileage by 7% to try and get an accurate figure. DTT upgrades (tc, valve body, update kit, and billet input shaft) will be here on Thursday, I hope that will help mpg some. I have been running a fuel additive, that helped mpg on my 01. What else could I do to improve mpg? (DDII's or BDII's are going in right after the DTT stuff).

 

[JBlock]

Never better than 18

My early 2001 never average much more than 16, but it does drop below 14-15 pulling up to 10,000 either/ 3. 54 4x4 2500

 

[redram]

With the large oversized tires, what rpm are you turning going down the road?



If the larger diameter tires have geared you down to where you're cruising below the peak torque, it could be hurting your fuel effieciency.



Just a thought.

 

[Chace TX]

At 70mph...

I am turning just to the right of the mark before 2000rpm. With these jukey tach markings it is really hard to tell exactly what rpm that is. If I remember right the ideal rpm is around 2100. At 2100 I will be going about 82mph, I think. My mileage was the same with the factory 265's if I am correcting right by multiplying miles X 1. 07. To go 70, and turn 2100rpm's, I would have to have some little bitty tires.

 

[LoneRam]

Chace,

I wish I had the answer. My mileage has NOT changed since I bought the truck new. As you can see in my sig it has undergone some changes, but with the same driving habits, the milage lingers around 15 +/- . 5 mpg. Granted my truck just turned 10k and I don't tow. I too am searching for better #'s. Good luck my friend.



LoneRam

 

[pwr2tow]

I have been on this board for almost three years and I have read alot of posts about MPG. It seems for the majority of the trucks that start out getting poor fuel mileage never do get better, mine included, a few do but not many.



I beleave it is an ECM problem and while I still had warranty tried in vain to get the dealer to try a new ECM with no sucess. We went through the process of elimination on many different things (even was sent to cummins) to try and figure out the problem but the dealer wouldn't budge on a new ECM. His reason was the ECM cost over a thousand bucks and he would be stuck with a ECM that he couldn't put on someone else's vehicle if it wasn't the ECM that was giveing the problem because then it would be a used electrical part and they don't sell used electrical parts.



It would be great if we could get someone that has a truck with good mileage and one with poor mileage and do a ECM swap to see if mileage numbers follow the ECM's.



Ron

 

[24V-DSL]

I've got 48K on the clock. First 35K I was always 14. 5-15. 25. Last 15K I've crept up to 16. 0 to 16. 75. Last bombs since 35K have been ATS manifold, AFE Mega-Cannon and Piers Nasty Nine HY. Guess I'll blame it on those. I'm not hopeful it'll get better, but it really doesn't bother me that much.

 

[Chace TX]

I would be happy with anything over 16.

If I could get a 16mpg+ with regular driving, I would be happy. This DTT upgrade might get me there. Has anyone else noticed more MPG with their upgrade. I just got the Mag-Hytech pan in today. Other parts are on the way.

 

[georgej]

Chace





I think the mileage your getting is ok. 14. 5 mpg out of a 7000lb vehicle seems good to me no matter what others claim to get! One of my cow-orkers gets 14-16 out of his Ford ranger, now thats crappy mileage.



George

 

[Chace TX]

Your right.

14. 5 is ok, I would not worry about it if the PSD's were not getting close to the same with a V-8 diesel and other CTD guys were getting 20+. I guess I would like to have my cake and eat it too. I just want to take every opportunity to help it get more MPG.

 

[Devildog]

I only get around 10-12 MPG



But I drive like a Mad Man!



Just weighed my truck Sunday, 7420lbs. with me (220) and a full tank for fuel.

 

[CoreyPerez]

My new 02 with just over 1000 miles is averaging (OH Console computer) 14. 6 mpg. I really liked the 12v I had as far as economy, but I hope it changes after breakin...



Corey

 

[Piston Slapper]

It may not be broke it yet...

my dad has a 98 3500. It is only used for pulling a 38ft enclosed trailer with a 1939 chevrolet show truck inside. He always averaged about 13-14 pulling the trailer . Has driven it twice without the trailer and it got 15-16. He just passed 38,000 miles and started driving it more cause he wrecked his daily vehicle. It just started getting 15-16 loaded and 18 empty. I used to rag him all the time cause mine gets 20-21.



I think it just took it a while to get it broke in. He says it's hard to get it below 15 mpg now... He has the heavy foot disease we all have!

 

[kaptn]

My truck was getting 15 mpg new. Went to 16 with DD1 injectors than 16. 8 with DTT upgrade on paper. My digital readout went from 16-18 mpg. Oh by the way I am always in race mode (lead foot).

 

[Camara]

I'm new to the TDR Joined about 2 weeks ago. This is one of a few subjects that gets me going. I had a 1995 2500 QC 4x4 SLT all stock, it got 22 MPG. I just got a tank of fuel about an hour ago in my 99 and it figured out to 13. 4 MPG. When I first got the truck it averaged 18 and has been going steadily downhill since. I've had it back to the dealer for this problem. After almost $ 400 they told me it was a bad battery that was causing the computer to see low voltage and causing the bad fuel mileage. BTW it only took me 3 days to get the dealer to change the lift pump last weekat 70,000 Mi. Another story for another day. :-{}

 

[IdaH.O.Train]

I never really tracked my mileage at first; however, with the mods I have I can get just over 20 mpg @ 70-75 mph. With some combined city driving it drops down a few mpg.

 

[Turbo Horseman]

Suggest you check the following in any disorder you wish:



1. Some kind of fault may exist in the relay between your foot and your brain.

2. Your speedometer may not be adjusted for the size of your tire footprint.

3. You may be telling the truth about the mileage... which means...

4. How black is your exhaust when you pass the knob who cut you off and he has his window open?

5. Your calculator may be lying to you. I find they do that very often until I have reinterrogated it... sometimes I have to do that alot.

6. Verify that the number of fingers on your hand when you wave with is greater than the number of fingers on the hand waving back from the P/S as you blow by it.

7. After that, did you go back and give the Duramax guy a tow to the shop?

8. Are you using the U. S. gallon instead of the gas mileage friendly imperial gallon? It also conveniently shrinks the size of your fuel tank at no additional cost.

9. Have you been idling yourself to sleep at night?

10. Do you know where your keys are at all times? Wives and girlfriends say they don't like our trucks... maybe one of them has been fooling around with your truck behind your back.



Depending how you answer these questions may determine whether you have issues needing some form of therapy. It may be you have been induced into a self-loathing disgust because of what you think is poor fuel mileage.



Go to your safe place and think about this: it is not how far you go on each gallon, but how much you get out of each gallon as you go. Oo.

 

[MCummings]

Originally posted by Turbo Horseman

Suggest you check the following in any disorder you wish:



3. You may be telling the truth about the mileage... which means...



5. Your calculator may be lying to you. I find they do that very often until I have reinterrogated it... sometimes I have to do that alot.



it is not how far you go on each gallon, but how much you get out of each gallon as you go/

OH MAN, I'm falling out of my chair, my stomach aches, and my eyes are all teared up,, That's the funniest thing I've read since the "Fart" thread".



But it is oh, so true.



I get about 12. 5-12. 8 no matter how I drive,, When I drove from Laredo, to Houston to Dallas, and Back to Laredo I averaged around 12. 5 - 13 MPG.



Don't worry about it not all trucks get good MPG,, be carefull about low MPG numbers,, some people tell the truth



Just put an Edge COMP, some HUGE injectors, and look at the overhead computer for mileage,, that'll make you happy



The smiles per mile,

Merrick Cummings Jr

 

[Dave MacArthur]

Chance,



Are you calculating the mileage by hand or using the computer? My computer is always off. Also, have you checked your odometer against a GPS or roadside markers? If you do the markers, do it over a long distance. At least 10 miles. 100 would be better. Do you always use the same station to fill up? How do they check the accuracy of the pumps in TX? Here in MD the Dept. of Ag. checks them for accuracy. There have been plenty of fuel dealers busted for cheating over the years. If you use the same station all the time and they are cheating, that could be your problem. Also, some stations tend to have a lot more water etc. than others. Do you have to drain much water our of your fuel filter? I have a '99 auto, 3. 54 gears. I also have the Comp (5k miles) without the wire hooked and I have averaged 17 m. p. g. for 75K miles. That is without towing and running empty most of the time.



Dave.

 

[Chace TX]

I use my pencil and a calculator.

I do not have a mpg computer on my ride. I fill up at the same station, always have. It is the Coop, and their pumps are accurate. I have not checked the speedo against mile markers, I will do that this weekend, when I drive to Lubbock. I have been adjusting the miles by 7% to make up the difference from 265's to 285's. I will order the speedo gear and put it in when I have a little time. I got it right on my 97 (speedo gear in transmission to accurize the speedometer), hope I can get the right gear for this one too.