Why does my mileage suck goats?

[RobG]

I was talking about this in a thread about my aftermarket fuel tank (which got moved to the Towing area), but my fuel mileage is really awful. It's been awful since I got the truck, and I'm getting annoyed.

Unloaded, commuting, I get between 13. 5 and 14. 25 mpg, and that's adjusting for a 4% odometer error caused by the 19. 5" wheels and tires. Today, I drove from here in the Bay Area, to Bakersfield and back. Unloaded, on the way down, running 80 mph with the cruise on, I averaged 14. 23 mpg. On the way back, running at 75 mph with the cruise on, I got my highest ever of 14. 57 mpg. Still absolutely pathetic.

With my camper loaded, driving normally (without cruise, going with traffic), I get 10 mpg. With the cruise set at 65, I got 12. 3 or thereabouts. Hardly stellar.

The truck has 6000 miles on it as of today, and I've done at least 1000 miles worth of load-carrying since I got it.

Is it realistic to think that the mileage is going to suck this badly until I hit around 20k? I just don't really see it going up more than maybe two more points, which is where it SHOULD be now, I think.

I'm starting to think it's time to unplug the EZ and start complaining to the dealer.

Rob


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2001. 5 RAM 3500 QC 4x4 ETH/DEE Silver/Agate 4. 10 USGear OD, Rickson 19. 5 Wheels, Edge EZ, SPA Guages, Psychotty, Firestone Airbags, Hellwig Rear Swaybar, Torklift Superhitch & Camper Tiedowns, Mag-Hytec Diff Cover, DD 4" Exhaust, US Gear Exhaust Brake, etc.

 

[PUFF00]

Rob,

Mine is 2 days old (250) miles. My trip computer says 14. 5 average. I'll keep you posted on how mine progresses.

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Black 2001. 5 3500 QC 4X4 6-speed HO
Black 1998 Jeep TJ (almost street legal) http://www.nm4w.org/members/puffer.htm

 

[RobG]

Don't trust your trip computer. Mine also gave me a load of crap like that. My trip computer has NEVER been accurate, not even close. You're better off using the odometer and how many gallons it takes to fill up. That's what I use.

Rob

 

[PUFF00]

I agree in general, but my last truck's (2000 V10 2500) trip computer was very accurate--within 2%, most of the time, of what I calculated.

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Black 2001. 5 3500 QC 4X4 6-speed HO 3. 55
Black 1998 Jeep TJ (almost street legal) http://www.nm4w.org/members/puffer.htm

 

[Whitmore]

ROBG,I would get with a friend and do a comparison for your mph on the highway to make sure your adjustment on the computer was correct. I get 20 to 21 at 68 mph all the time unloaded,I have found that any speed past 70 and my mpg goes down Kevin

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2001 eth dee,qc,lwb,3. 55,camper and tow pkg,driftwood,cummins e-brake,jardine 4" exhaust,dz alum checker run boards,bed rail,tailgate protector,better built alum checker toolbox with home made fuel tank under box,"CUMN" licence plates and captain vol fire dept plate too

 

[PUFF00]

Rob,

I'll be calculating it and also keeping track of how accurate the trip computer is. In any event it will be interesting to see how my milage averages out compared to yours. I'll post back here in a week or so and let you know.

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Black 2001. 5 3500 QC 4X4 6-speed HO 3. 55
Black 1998 Jeep TJ (almost street legal) http://www.nm4w.org/members/puffer.htm

 

[arlan]

Rob,

The expression I've always used is "Blows Goat". And my mileage does also. I have 70,000 on my truck and 69,000 of that have been with my slide in camper in the bed. Best milage I have ever gotten with the camper was
13. 9 and worst was 9 something. I seem to average somewhere in the 11's. It used to bother me a lot, now I have just come to accept it. Others say that a slide in is the worst possible for mileage and when I stand back and look at it, it is an aerodynamic nightmare. I still love the truck and camper and it hauls *** .

I also have the Rickson 19. 5's and the adjustment for my tire size is 5. 5% checked with GPS and mile markers. Mileage was the same before the 19. 5's and any power mods. I haven't really checked it enough with the camper off to make a statement on empty mileage.

Arlan

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98. 5 ISB QC 3500 4X4 3. 54, PowerMax1, DTT TC & VB, TY303 225/70/19. 5's on Rickson Wheels, 275 Injectors, Mag-Hytec Transmission Pan/Differential Cover, 9000 LB Warn Winch, Ultra Board Running Boards, Westach Combo Boost/EGT Transmission Temperature & Fuel Pressure gauges, Pac Brake, 2-lo kit, CB, GPS, Rancho 9000's, ATS exhaust manifold, JRE 4" exhaust with muffler and resonator. Lifetime NRA Member

 

[RobG]

Yup, blows goats is one I often use. I also might say something sucks donkey nuts through a straw. But that's really best left for another topic. #ad


I was just figuring out the exact correction factor for my wheels, and it's just over 3%, not 4% as I was guessing before. I know that at any given speed, my actual speed is 2 mph faster than indiciated. This is verified via GPS.

Rob

 

[Cheska]

I don't understand how certain truck's mileage goes WAY up after 15-20,000 miles. I've got 14,900 on mine now, and the worst it has ever pulled on a tank is 19. 36. That was on the first tank. Since then it has slowly crept up to 20. 5, where it sits now-every single tank. Straight highway (640 miles in one day) it got a shade over 23. Anyway, your camper provides more than enough load to break that baby in. I would get it checked out.

dave

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2001 driftwood 5spd 4x4 2500 reg. cab

 

[RKohn]

Rob,

Yes, it'll get better, but you've got to give it half a chance. Don't blame the truck yet, either. (You must have missed issue 30. The subject of "establish a baseline" was repeated about a million times. ) Besides, 6000 miles is barely enough to wear the nubs off the tires let alone break the Cummins in. I don't expect you'll get too much better than a couple more though.

Hope you've got thick skin buddy, cause here it comes...

We're talking basic physics here.

After all the stuff you've added on your truck, it probably weighs twice what mine does. (ok, maybe it's just a 1/3 heavier) More weight=less mileage.

Add that camper and it's about as aerodynamic as the QE2. More windload=less mileage.

80mph? Windload increases exponetially with your speed. Double the speed is 4 times the windload. More speed=less mileage.

4. 10 USGear OD? Good idea, but a lotta bucks vs. a 3. 54. Granted, the splits are nice, but how much does that sucker weigh? Remember more weight=less mileage? It still applies, no matter what gear you're in.

EZ? I know you didn't put it on your truck because it looks cool. Regular use of nifty fueling electonics + close proximity of right foot to floorboard = much fun + lousy mileage.

Did we mention fuel? Even in Commiefornia you're getting winter blend and that's gonna hit you for 1-2mpg. Less BTU/lb. of fuel=less mileage.

But look on the bright side. You could have got the V-10, with almost the same power, a lot less noise, 1/3 of the life expectancy, and 1/2 the mpg on more expensive petrol.

Besides Rob, after the billion $$$'s you've spent on toys, what's a few bucks on fuel? #ad
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JMHO

Rick


btw - Bombing slowly along, one step at a time. Turned 44k today. I also cruise @ 80mph. Getting 16. 5mpg lately, 18. 2 avg since day 1 (actual calculated).

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Y2K Red Stealth Sport 2500 4X4 QC SLT+, 5-spd, 3. 54 anti-spin, 265-75-16 LTX’s (There ain’t no such thing as options, cause ya gotta have it all, including: DC’s dead cow/vinyl interior and don’t stop anti-lock brakes. ) Stock, but not for long. Oops, too late. What silencer ring? (More fun than my 98 SST)

 

[pwr2tow]

I have studied alot of posts about MPG and my conclusion is if you are getting poor fuel mileage after approximately 3,000 to 5,000 miles you will more than likely never get good mileage. My opinion is the normal mileage is 14 to 16 MPG highway and 7 to 12 MPG towing (varies by weight). Out of 6,700 members to the TDR you might get 40 or so people to respond and they say they get great mileage with a few poor mileage reports inbetween. My theory is everyone reads someone gets 20 MPG and then the ones with poor mileage are too embarassed to report. If you look close at some of the threads you can see there are some of us out there that will report bad fuel mileage. I do agree there is something wrong if a truck is getting terrible mileage, just have not figured it out yet. There was a guy on this board who was getting terrible mileage and his truck shelled out on him, he had it rebuilt by cummins and know he reports he's getting great mileage. The moral is if your neighbor is getting good mileage a person tends to stretch the truth a little. I know some claim to get great mileage and some do, just not the average, if these mileage claims where normal chrysler corporation would have it on their average MPG stickers, yet they make no claims to mileage. Go to your dealer and have him put what the average MPG should be in writeing and see what you get. If he does then make him own up to the mileage but he won't give one, why, because the truth is these trucks do not get as good of mileage as some claim (the high mileage is more of the exception than the rule). I'am not trying to flame anyone thats just my opinion. I know of three 24v in my area and we all get about the same. On the computer you can'nt see someones face to tell if their fudgeing on the figures a little. My hats off to those who are getting great mileage. Hell i even got 99 miles to the gallon once (I was going down hill with my foot off the throttle and reset the computer). By the way I keep a log of miles driven and fuel used, calculate by hand and have had my speedo verified. I may sound ****** , maybe I am or maybe I'am one of the average (still checking posts and doing some experimenting on my own). Ron

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1999, 3500, 6x6, slt, auto, 3. 54, Qd cab, ISB cummins, towing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner.

 

[Shovelhead]

Reading some of these posts about fuel milage makes me feel alot better about mine.
Averaging 14. 7 mostly in-town (Wash. D. C. traffic) With a couple of long (2-3 hours drives) at 65+ reaching 16. 1mpg. Running unloaded, using cruise control, tailgate up. This still beats my old '90 D150 w/ 318 FI and auto that got maybe 14mpg on a road trip.

 

[willyslover]

Hey Rob. . the man with the one word dictionary. . "Sucks" used as an adjective, noun, pro noun, verb,adverb ect ect #ad
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[just kidding]

I just turned 10k in my 3500 4x4 6sp. . been seeing 14. 5 to 17. 5 [most in the 16+ range] drive 71 miles to work one way start at 4000ft go to valley floor 100ft. . plenty of twisties ,about 1/2 of the drive thru mountain roads. . milage is directly proportionate to the foot position/fun factor, so I would say your mpg is on the low side also . .

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Ol'#2 '01 3500 ETH/DEE Q/C 4x4 SLT+ sport silver.
NRA

[This message has been edited by willyslover (edited 03-11-2001). ]

 

[LSMITH]

Rob, I know a guy that had a 99 24v auto w/4. 10, highest he EVER got was 14,averaged around 11. My 99 has auto and 3. 54 and 285's and the lowest I have ever seen is 17 calculated. I think that there is something wrong if you cannot get at least 16 driving like a grandma. I drive mine very easy to get the numbers I do. I am sure if I had a heavy foot for a full tank I would be WAY down from normal.

 

[thepitts]

I run about 10 miles to work one way, I average about 15 MPG. The last tank had lots of foot stomping and came in at 13. 5 MPG. I also use the PS additive that boost the cetane on winter fuel, seems to help. I have 4:10 gears and just put on 285's, so who knows now what will happen. And as always your milage may vary #ad


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Eric Pitts 2001 Properly Valved 2500 Qcab 4X4 auto Transgo shifts it 4. 10 LSD Weston Nerf Bars Smith built brush guard Command Remote Starter Scotty Air DD stage 1’s, PS boost module , elbow 32psi boost 247hp,657tq Neophyte B. O. M. B. er
The Pitts Home Page
Member GLTDR

 

[BNSF # 1]

I keep track of every gallon of diesel that has ever been put in the tank of my Ram and after 9700 miles my average MPG is 18. 6

This is mostly back and forth to work driving at about 60 to 70 MPH, unloaded. I have come to one absolute conclusion about the ETH in my truck. It is not very economical at engine speeds above 2100 RPM in my truck with a 4. 10 final drive ratio.

I am very satisfied with my mileage average of 18. 6 MPG considering that my truck weighs over 6500 lbs.

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CJ in RSM, CA
2001 Dodge Ram 2500 SLT Quad Cab, 6spd,ETH,4x2,4. 10 Limited Slip, Trailer tow hitch, long bed

 

[Vaman]

I got 20-21 until the EPA and Dodge decided to reprogram my ECM... after that it dropped to 18-19 (really pi**ed me off). Anyhow, for you guys getting around 14, it sounds pretty low. One guy claims he's getting like 26... I would be looking at possible causes. Good luck.

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98. 5 2500, 24v, QC, 4x4, 4. 10 LSD, short bed, Line-X liner, tow package, camper suspension, Westin nerfs, camper shell, TST PowerMax3, 275 RVs, EGT/Boost pillar gauges... Love my Cummins, no love for Dodge

 

[J Allan]

I checked both, my miles and fuel used and my computer they where on the money. (before bombing part), Towing my trailer (total truck and trailer weight 16,400 lbs)I was 9. 5 to 10. 5 . Running solo, I average 16 to 18 depending on speed. Now after bombing part, my computer was way off, it was saying I averaged 16. 5 after pulling my pig of a trailer. I wish that was a true reading. #ad
Then I could tell momma that all that money I spent on bombing, paid for itself because of the fuel saved.

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Jeff Allan
31D 81199
2000, 3500,4x4, 355 gears Laramie SLT, BD valve Body, BD Torgue Convertor, BD pressureLoc,#14cm wastgate turbo housing, powermax 3 adjustable, stage 3 injectors, custom dual 3" exhaust with dual 4" barrel tubes behind rear tires. Trailmaster SSV shocks, ISSPRO Turbo boost, EGT gauges in piler, K&N air filter, bushwacker fender flares, black nerf bars, hellwig spring helpers, Let the BOMBing begin

[This message has been edited by JAllen (edited 03-11-2001). ]

 

[RonaldLarson]

Eighty miles per hour with 4:10's and you are complaining about fuel mileage?
Ron

 

[DocStressor]

GKohn is correct. It’s largely a matter of physic. Most of you guys drive too fast and too heavy to expect great mileage. Although the trip computers are usually not very accurate in absolute terms, they give a pretty good estimate of relative mpg for a given truck. I understand that the computers on the 2000 or newer trucks give you instantaneous mpg, rather than an average since the last fill up like mine does. If so, you should be able to determine very quickly for yourself the effect of driving at 55, 60, 65, 70, 75, and 80 mph. Pick a day when there is little wind to try it. The effect of increasing speed on mileage is dramatic. And the effect of speed is even more remarkable with a camper loaded.

It’s hard not to drive fast when you need to get somewhere. You can do two things that should improve your mileage at high speed: 1) Increase your tire pressure by 10% over that recommended for your load. 2) When running empty, put your tail gate down (but don’t remove it). RobG, a downside of your Rickson’s is that by increasing the clearance under the truck, they increase the drag coefficient of the vehicle. Since drag increases by the square of velocity, the effect is greater the faster you drive. I predict that if you follow both tips, you will get 17+ mpg at 60-65 mph empty, which is not too shabby for a 1 ton. The 3/4 tons get better mileage because they weigh less and and have lower rolling resistance with 2 fewer tires on the pavement.

BTW, I average between 14. 43 and 18. 5 mpg hauling my camper at 63 mph. I once ran almost a full tank at 70 mph and got 12. 1 mpg. Winds are a big factor, but the 70 mph trip was with very little wind. I get between 19. 7 and 22. 1 mpg running empty at 65 mph. Nearly all my driving is over hills and mountains.

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1999 Quad cab 2500, SB, SLT, 4X4, 5-speed, 3. 54, tow and camper package, Lance 820 camper, Lance cabover stabilizers, Rancho 9000s, Airlift airbags