Mileage... does this sound normal?

[cskemps]

So at 68 mile's an hour and around 2400 rpm with the stock set up i average pulling aproximatley 9000lbs. I'm getting around 9 miles to the gallon.Does this sound right to anyone out there. It's the truck in my signature. I've talked the wife into a Heath GLE ecm, Heath high out put injectors and a TM. Also she said when i start working full time i can get a ATT. I here people talking of getting up too 16 miles per gallon pulling ( i wish ) even when empty the best i've had is 12-13 mile per gallon.

 

[Tookie]

Probably pick up a mile or two by slowing to 60 MPH

 

[OregonHorseTug]

How many miles on the truck (or on the injectors)?
If I pulled that fast I'd get about 9 mpg, your setup isn't much different than mine save for the DRWs. I'll get about 14.5 at 70-75, empty, with my fresh injectors so that's not far off from yours if you've got over 150k miles (235km) on your injectors. I gained about 1-1.5 mpg with the injectors I have now over the originals; changed them at about 235k miles so they were probably pretty tired. I'm not ready to recommend 2700# injectors to anyone until I see if the pump lives for at least 50k. Now I get about 10 mpg when the trailer is loaded and I'm at 19k combined. I'm looking forward to the ATT.

 

[buddy]

Dually, 4x4, 4.10, 9mpg sounds about right.

The ECM upgrades are awesome, simply put, for power and can only help mileage.

if you really want more MPG, need higher gearing, like 3.73 which will still pull 9k lb. but at lower cruising RPM. Taller skinny tires in the back will effectively raise the gear ratio as well, reducing drag by getting the front end down a little would help, especially if the trailer pulls the back end down.

Thats because 2400 RPM is at the top of the power band, and to get good MPG need to be near bottom of the power band around 1800-2000 RPM. higher gear ratio will get you lower cruise RPM at the same speed.

 

[VW_Lupo_TD]

why the high output injectors with the GLE?
if I remember correctly heath recommends the HO ones with the GL4 and other mods only.

 

[buddy]

He has the other mods already

 

[DieselCash]

I get about 16 - 16.5 mpg in my truck empty. I have yet had a chance to pull anything with my truck as of yet. My truck is bone stock 2wd with a 5 speed trans. That would make a little differance compared to your truck.

I also agree with the above statement, the slower you go the better your mpg will get. Driving habits make up for a big part of your mpg also.

 

[mitchedo]

I would go with stock injectors if you're towing, and especially if you're concerned with MPG. Bill Heath told me the HO injectors make things run hotter (for my application), which you don't want for towing. Perhaps with a turbo master you could negate the extra heat. Ask Mr. Heath for his advice when you make your purchase.

BTW, in my 5.7L gasser Suburban V2500, towing 7000 lbs at 68 mph, I get 5 mpg. If I slow to 55, I get 9-10. But I can't drive 55. Want to improve your mpg while towing? Slow down so you're running at the rpm that is the torque peak for the engine (1900-ish, I believe).

 

[daustin]

With my '93 3500 dually, 2 wheel drive 4.10's i get 13.5mpg at 65mph towing about 8000lbs. If i go to 75mph i get about 10mpg, if i slow to about 55-50 i get 14-15mpg. Unloaded i get about the same, maybe 1mpg better which i think is more because of the 4.10's. I usually run with the cruise control on when i'm on the interstate as well, seems to keep my heavy foot out of it some. lol (I can't drive 55 either)
Don

 

[Acesneights1]

That's about all my 3500 gets under same circumstance and it's not a dualliee.

 

[Schwind]

I get around 13.5 to 15 MPG with my truck running about 65 MPH with the same size load. Thats around 2250 to 2300 RPM's with my 3.73 rear end and TCC lock up.

 

[68post]

I won't drive over 62 mph because of the drop in mileage @ the higher rpm's.
(10,200lbs empty, 4.63 gears ,2wd, and a barndoor size bulkhead).

My best is a city/hwy average of 15 mpg (55 to 60 mph hwy)

 

[Slim Shady]

When I hauled the 22000 lb load I did 1000 miles at between 65 and 70 mph along with start and stop city driving. Mostly highway and with the ATT turbo and a Heath HP-4 I averaged 11 MPG. through the whole trip. I have 4.10 gears and a five speed.

 

[nvmtnlion]

My truck with GM-8, WMI, 3.73s, and Heath HP4 got 11 mpg towing a Case Construction King tractor on a triple axle flatbed at 65, and 7 at 70 mph.

I never bothered to check the weight. Just way glad TD recommended the Prodigy brake controller.

 

[JiFaire]

Pulling 30' high-front 5er, 9800 lb loaded, I get about 14-14.5 on the level at 62 mph. As soon as I get wind (especially those nasty front-corner 45* crosswinds!), hills, or try going ANY faster than that, it drops like a rock.

Heath chip and TM actually helped both power AND mileage (gained about 1.5-2 mpg loaded!), but my right foot seems to be the biggest factor, and it's connected to my lame brain.

Strangely enough, I get worse mileage if I go slower, too... 55-60, my truck has issues with pulling and will drop in and out of Lock if I don't have TCC locked... every little rise and it shifts, seems like it's lugging at 55... If I go just over 60 it's better. Anything over 65 it starts to go down again.

Every truck has it's sweet spot, the speed/rpm where things run cool, EGT stays down, mileage is just right, power is OK... find yours and drive on it, even if you don't like the speed.

 

[Detroit Dan]

When I had stock tires, my 97 dually got 13.75 no matter what I did with it. Towing 11k under 65 got 12.5 to 13. Always amazed me that the towing had virtually no effect on the mileage.
I have since upsized twice with the tires, so now I have no idea how far I am going on a tank, since my speedometer and odometer are off. New injectors and exhaust probably gained me a bit, but lift kit, aggressive tires and a big old light bar mounted on the backrack above the roof doesn't help.
I definitely see a huge difference if I push it on the highway. 60-65 is ok, but if I try to do anything above 70 I'm out of my trucks comfort zone and she sucks the fuel down like crazy. Of course, I don't know how fast I'm actually going, and the taller tires lower the gear ratio (numerically) so in actuality I've probably gained a tad more speed that I can go.

 

[buddy]

If you use the ratio of the stock tire height to the new tire height you can use that ratio on the odometer and speedometer. like 33" New/29" old x speedo reading, so it gets more off as you go faster.

Do OBD-II use a VSS and VSSB module like in OBDI? If so might be able to change it out for one that would make speedo and odometer correct.

 

[Detroit Dan]

If you use the ratio of the stock tire height to the new tire height you can use that ratio on the odometer and speedometer. like 33" New/29" old x speedo reading, so it gets more off as you go faster.

Ow, math hurts my head!

 

[chrisk1500]

cskemps - you also need to realize that in our little part of the world, we are still using winter diesel.

Once they bring us the summer diesel you will see MPGs go up 1-2 MPG....the drop in MPG sucks, but I have never had the winter diesel fully gel up on me (that's a good thing!)...

 

[SnowDrift]

So at 68 mile's an hour and around 2400 rpm with the stock set up i average pulling aproximatley 9000lbs. I'm getting around 9 miles to the gallon.Does this sound right to anyone out there. It's the truck in my signature. I've talked the wife into a Heath GLE ecm, Heath high out put injectors and a TM. Also she said when i start working full time i can get a ATT. I here people talking of getting up too 16 miles per gallon pulling ( i wish ) even when empty the best i've had is 12-13 mile per gallon.

Seems low to me, but at 68 mph, she's spinning a good clip. Bring it down a notch and see if 60mph makes a difference for you. Unless I really load up, my mileage doesn't really ever change. Bone stock to now running bigger rubber, visor, added weight on truck, etc. it's still 13-15 mpg or so.