2001-early 2004 LB7 Duramax Fuel Economy Poll

[mhagie]

Bought truck last saturday(10/29/05)in central Indiana drove it home to SE Iowa 439mi @ 19.4 mpg
Not going to complain.
Merle

[TRPSHOOT]

Alright this isn't scientific or anything but this is what I came up with. I just drove from near Indianapolis to near Gunnison, Colorado for our annual elk trip. I reset the computer stuff to zero on the personal trip option (DIC).

I have 22,000 miles on my extended cab 2003 with 265 tires.

I weighed the truck empty and with trailer, full tank of fuel each time.

Truck weight with tool box, full tank of fuel, and no people= 6700 pounds.

We ran about 66 mph out there and according to receipts and old fashion math that = 17 mpg. Oh yal the utility trailer is a dual axle that we stuffed 3 quads on with other junk for a weight of 5200 pounds loaded.

Total round trip= 2634 miles

computer says = 14.0 mpg average

receipts and my math say = 14.8 mpg

average mph = 48

computer says 188.3 gallons used

receipts say 190.5 gallons used

There were about 10 times in Kansas that we were bored and kept the spedometer on 60 mph and then started the timer at the mile marker, consistantly we were at about 58 - 59 seconds. So if the spedometer is not already calibrated for 265 tires, then it is pretty darned close.

We were camped at 10,000 feet so says the GPS units we had. I took the truck back on some pretty rough 2 track trails with some really steep hills. The DMAX never missed a beat and I love that allison how it holds it's gear going down severe grades and hills.

The only thing was that when I first started the DMAX in the morning, it would smoke until engine warm up. I don't know if this is a faulty glow plug or what. Temp was around 19 degrees before sunrise. No smoke after engine operating temp was obtained.

The tranny temp stayed below 200 the whole time with the exception of the last 5 miles of the trip going up some really steep 2- track trails pulling the trailer.

This is a stock truck.

I am thrilled with the performance of this truck.

P.S. The Ford 10 cylinder gasser that accompanied us, got 8 mpg towing a 1700 pound pop-up camper.

[sjd_sd]

My mileage ranges from about 16 to 20. 16 happens with lots of 4wd use, deep snow and slow driving. 20 happens at a steady 65-70mph on the highway. I have a camper shell and one-size-up from stock tires. The price of diesel makes me wonder if it was worth it. Fuel for a gas-burner is about 40 cents less locally, so its almost a wash.

[schaack2]

Just checked my 2003 crew/short box today and I got 17.3 - only current mod. is 4" exhaust. This tank I just check I had been pretty heavy on the throttle with a lot of town driving. Previously checked tanks were high 18 / low 19 (all calculated manually).

After reading through all the differences in fuel economy, I'm curious which variables make the biggest difference in fuel economy. I've got a laundry list of upgrades to make, regardless of economy, I want to make larger burn-outs!!

How much affect do you guys feel a bed cover or topper makes on fuel economy? I've never had one on a truck but it has to significantly reduce drag (at least one would think). After reading all posts, two of the guys with the best economy had either a topper or a bed cover. What are the thoughts of everyone else on this matter?


Schaack2

[SDakDmax]

19 to 20 going 55 - 60 no problem, if I get my foot into it and go 75, it will drop to 16.. I think this is good.. the best part is the power when you get your foot into it, and towing..

[diesel dissapointed]

I hope this post saves some poor guy from thinking he can get the mileage #'s some of you guys are posting.I am on my second duramax after lemon lawing my first one.Total mileage over 100k and neither truck ever saw over 17mpg,that includes empty, downhill,tailwind,drafting,etc.This is a reg. cab 4wd 9,200 gvw truck that usually runs 65-75 with cruise control @ sea level.P.s.I've been a professional mechanic over 30 years and this truck has been on the dyno and had parameters checked with a tech 2 @.worst mileage was 9mpg towing 10K lb boat

[muncieman]

I have a 2003 Chevy 2500HD crew cab with the allison and my truck has gotten 19.9 as an average for 65,000 miles. It has on several trips been in the 24 mpg rage. It is a 2 wheel drive version and bone stock.

Now if we could just get the lousy fuel companies to charge a decent price for the fuel

[BozDMAX]

I first noticed the difference between the DIC and my actual mileage in March '05 and have been tracking the difference since then. After throwing out some obvious outliers I ended up with 106 data points and using a least-squares/best fit methodology can pretty much estimate my actual mileage by the following formula:

Actual MPG = .86*DIC MPG + .74
R-squared (if you remember your statistics course) is .86 - not terrible given the wide range of conditions (towing vs. non-towing, hills vs. flats, changing altitudes, etc).

so, 20 MPG on the DIC would work out to about 17.9 on my slide rule (anyone else remember those?) with the actual data.

All the data is after the Banks system. No idea if the early data for the first year before the Banks was more reliable or not.

You can take the retiree away from cost analysis, but you can't take the cost analyst out of the retiree...:-)

[More Power]

2001 GMC 2500HD Crew cab shortbox 4x4 LB7:

1820 miles - round trip from western Montana - Las Vegas SEMA show. Each 910 mile leg took 13 hours and 20 minutes, for a 68+ mph average speed (which included fuel & convenience stops). Where possible, the truck's speedo hovered around 85 (65 through Salt Lake and in the mountains north of Salmon, ID on US-93). Calculated fuel economy for each tank ranged from 18.5-mpg to 20.2-mpg. Best tank was the last leg from Idaho Falls, ID to Missoula, MT. Just me and about 100-lbs of gear in the truck. The 265 Michelins were aired to 70-psi front and 60-psi rear. Mobil Delvac 1 synthetic in the engine. Power Service fuel treatment used at the recommended mix ratio. One tank was B5 (Sinclair station in LV). Otherwise, all tanks but one were ULSD. And.... the VanAaken module was turned off for the entire trip.

Jim

[SoTxPollock]

Pretty impressive running 85 averaging 68+ and 18.5 to 20+ mpg. Your truck is right in every way. I may be able to come close to that. I've made 17.2 at 92 and 22+ at 63. I could never drive 55 for a whole tank full, would probably fall asleep. I'm suprised to find out it hasn't dropped below 17.3 with juice on level 4 for a month now. I think my truck thinks its a corvette the way the engine responds, but amazing that the mileage isn't hurt much. My lifetime average for 90,000 miles is still in the high 18's. Great Truck. I've been running the exact same air pressures you have too. However I'm having to back that down now, they're showing wear on the center more than on the sides. Noticed it more on the rears, but I know why.

[colt49]

1. MPG
   Mileage is constantly 22 or 23 on highway In town is20 or 21 4K miles #2 fuel Flying J Cheyene Wy.06 LBZ 4x4 Allison Reg. Cab

Flow Pro Exhaust 4.5" Stainless EDM Fits

[2500HDTalley]

I was getting 13 average. Did some research as I had a problem the dealer mech's couldn't find. Lead them to the fuel injector area and they found my injector pump had gone bad. Once this was fixed I got 18 average. Dropped from 15w-40 synthetic to 5w-30 synthetic for the winter and am now getting 19.5 average.

[Idahobidcaller]

I have been getting 16-18 around town and 20 highway on my '01.

[reparkerjr]

Mileage is greatly affected by driving conditions. I get 16-18 mpg driving in town stop and go. On the highway I get 20-23 mpg depending on speed. My best was towing a 6 ft utility trailer at ~ 50-55 mph descending from 8000 to 6000 feet in 200 miles; I got 23.2 mpg. Typical is 21-22 mpg at 60 mph decreasing to 19+ mpg at 70 mph.

reparkerjr

[npauli]

I just bought my first diesel (see sig). The first full tank I ran was maybe 1/3 on the highway at 60, 1/3 in town, and 1/3 interstate at 70. I got 20.5 mpg!!!

I'm thrilled with my LB7, especially since the miles/dollar work out to be only about 10% worse than my gas truck, despite being 3' longer, a bit taller, 4wd, and a good ton heavier.

[Fightfan]

I've owned a few trucks for my remodeling company. I had a 97 GMC 1500 Z71, an 88 chevy 1500 extended cab LB, a 92 GMC 3500 Vandura with 6.2L N/A, and my 01 Silverado. Hands down the two diesels were much better all the way around. I could easily get 450+ miles out of my van on the highway. I've just done the upgrades to my Silverado, so I don't know what the mileage is yet after the fact. Bottom line: WOOOHOOO for Clackers!

[JDiesel03]

My 2003 LB7 (3500 4x4 dually)with breathing enhancements(ram air and 4in exhaust) just did 2500 mile mostly freeway trip largely on cruise at 75mph for overall round trip average of 19.6mpg. Lightly loaded with about 1500# of gear in the bed. My mileage starts dropping rapidly at over 65mph....trips holding to 65mph have netted me typically about 24mpg. Love it!

[Dek Hawkins]

I have a 2500 HD DMAX, 2002, and drive it in England.
I can say it does 27mpg on a 100 mile motorway trip @ 70-80mph,
or 22mpg dodging around.
I know many 4x4 owners who get less from their 2.0L diesels.
I would never swap it. I want a fifth wheel camper to haul, but need to get one from States ??

[Ian7]

I have a 2500 HD DMAX, 2002, ... it does 27mpg on a 100 mile motorway trip @ 70-80mph,

Given how far from 'typical' that number is, may I ask if that was a single 100 mile trip and tank top-up when you got there? I guess what I'm saying is that the top-up may have shut off very early and given a false economy?

or maybe a 100 mile long downhill stretch? :-)

(yes I know imperial vs US gallon, still 24+ in our context)

[chessy56]

Without a head wind, running ~57-60mph, mostly empty bed, I'm doing about 22-23 mpg on the highway. Depending on the severity of the head wind, I'm around 19 highway. Most trips are WI to mid IN.

Currently, I'm not getting Chit- truck appears to be down with head gasket issue. 400,700 on the odometer. Sure would like to upgrade to something newer, but a drop in fuel mileage would blow....

What's funny is watching the 50 mile average fuel economy with my Edge monitor plugged into the diagnostic port. Going through Chicago (I-94/I-294 with the sound barriers/trees/buildings blocking most wind), the Edge reported as much as 50 mpg! Bite me! Calculated value and not real, I realize. Still amuzing to watch.