2004.5+ LLY Duramax Fuel Economy Poll

[JD Diesel]

2000 on LLY 14 t0 16 Lot better than my 2500 sub with 454 vortec 9 to 11

[reedpilot]

I have a brand new 2005 2500HD with almost every option and I am getting 15.8 around town and 21.9 on the hwy. What are people using to increase fuel economy?

[REDTRUCK05]

I have a brand new 2005 2500HD with almost every option and I am getting 15.8 around town and 21.9 on the hwy. What are people using to increase fuel economy?

I could only wish to get that!

[EZHAULER]

I consistently get 15-16 mpg around town driving. (Easy with the foot-driving). I do not do much long Highway driving without a load- but with my toyhauler loaded 12K+ I consistently get 8-9 mpg @ 70-75 mph. I got as high as 11 mpg once trying too increase by driving 55-65mph. ALL hand calculated- filling up till I could see it in the neck. I'm going on a 1600 + mile trip next week, First trip after installing upgrades-EDGE Juice W/Attitude monitor & Cat back exhaust. After getting alot of info off the forum EGT/MPG. I'm going to try and use control and see how good it can get. Follow up info in a cpuple weeks.
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2004, LLY 2500HD,CC/SB 4X4,Edge Juice W/Attitude Monitor
MBRP 4"Cat Back Exhaust,K & N Air Filter,60 Gal Aux Fuel Tank
Sprayed in Bed Liner,Firestone Air Bags,Front End leved W 305/50 R20 Tires

[AndyU]

I took delivery March 31. I have about 3500 miles on already. I get around 17 in the city and as much as 21 highway, unloaded. Average unloaded highway mileage at ~75mph is between 17 and 20 with wind conditions making a big diffence. With a tail wind I will break 20. With a head wind... 17. Same pattern pulling my gooseneck horse trailer. Anything from 8.5 to 11.5 depending upon wind conditions at 65 to 70 mph. The trailers pretty big and heavy though, 8' wide about 9' high x 34' long, fully enclosed aluminum and stainless steel. 2-3 horses, water and hay add another 2-3 thousand pounds.

I just bought a Predator and on Sunday I loaded the 40hp tow program. I pulled my horses on a little 160 mile trip and the DIY said I got 11.8 pulling into a head wind @65-70 mph. Not bad I thought.. about 2 mpg better than usual into a stiff headwind. Next I unloaded two horses and reset the DIY. I then pulled my empty trailer another 40 miles down back highways at 55-60 crossways to the wind. It said I got 16 mpg. AWESOME! I thought (about 4mpg better than usual!). Finally, I dropped the trailer, reset the DIY and ran another 40 miles with the just the truck at 75 (no wind by then) and the DIY said I averaged 25mpg... that's when I got skeptical... to good to be true. I drove to work and back today, another 20 miles (I usually get about 17 to work and back). I refilled the tank and it took 21 gallons. 260 total miles / 21 gallons = about 12.4 average mpg. That was obviously way off. It should have used about 18.7 gallons according to the DIY for around 13.9 average mpg. The DIY used to be accurate within about 1/2 mpg and usually showed less than my actual. Now it's way off the other way. Despite the impressive computer reports, my real fuel economy appears no better...

Does anyone know why the DIY would get so far off? Does the predator change the calculations?

I'm going to continue testing for another week. If the predator provides no improvement over stock economy, it's going back. If I can get an extra 1 mpg or better, then it's well worth it, especially since it won't over stress my truck. The simple 40 hp tow program is as hot as I care to get.

I really baby the truck when I'm driving, soft stops, soft starts, rpm never gets above 2500. I really drive to maximize my fuel economy and equipment life.

Has anyone else seen improved fuel economy with a programmer? I have a friend who gets 23 with his 05 stock cummins and 15 pulling a trailer like mine. I'm on a real quest to get similar performance.

[okeehandyman]

have 2 '05 2500HD 4x4, 1 c cab 6' box & 1 ex cab 8' box. both getting 17-18 intown & 21-22 on out of town trips around 60 mph. about 1.5 mpg less per 10 mph faster. the fact is you have to decide how fast vs how much fuel to use. no free lunch, remember.

[AndyU]

Well, after thorough testing, towing, empty, highway, city, etc, my mileage went down with the Predator. Running empty, I lost about 1.5 mpg in city driving and about the same loss highway. Towing was about the same, maybe even a bit better, but it's hard to tell because of the affects of wind direction, rate of travel, etc which makes it hard to get a good baseline. The Predator caused my DIC to indicate my mileage went way up, but hand calculating my fuel usage revealed that in fact it went down. Very disappointing.

After restoring the factory program I averaged 19.5 mpg on a 550 mile trip last weekend (empty at 70 mph w/ cruise and a tail wind). I got 22 mpg on the last 100 miles (empty, no wind, 60-65 mpg w/out cruise) after refueling. I think that's pretty good.

The truck definitely gets better mpg w/out cruise on, letting the truck slow up a bit ascending hills and speed up a bit going down. Also, if I keep it at 65 or less my mpg is much better. Also no hard acceleration.

I only have 5000 miles. I'm very happy with this truck.

[57CHEV]

I consistently got 16 with my 02 LB7 and 14 with my 04 LLY all in town driving. Exact same trucks except one was a Chevy & one was a GMC.

[bamabadboy]

19.8 MPG on a 800 mile trip. Unloaded, all stock, air on, driver only, bed uncovered, 65-70 MPH all the way, 271 miles on the odometer at start.

[Shorty]

Purchased 2002 HD 2500 DA crew cab in Jan 05 LOVE THAT TRUCK getting 18 average empty around Texas.Came to Colorado towing 28ft. Jayco got 12mpg towing trailer. purchased Predator installed 2nd highest economy tune getting 20 mpg average.went from Grand Junction to Ft. Collins about 600 miles average 21 mpg best I have done so far. Haven't tried towing yet. EGT got around 1200 going over Vail and Loveland passes had to ease off of cruise to maintain EGTs

[RodneyRam-jet]

I picked up my '05 K2500HD CC SB 6/13/05. Used 18.895 gallons to go first 270 miles. I will fill up tonight or tomorrow on second tank full. That puts me at 14 mpg on first tank and I can tell I am doing better on second tank. Taking my first trip towing in two weeks. Does anyone use fuel additives? Any recommendations? I heard it's good to use during break-in.

[G Slaton]

I have an 05 CC 2wd Duramax/Allison. This is my fourth Duramax. By far the 03 got the best fuel mileage and ran just about as good as the LLY. I hae driven several LLYs and all run better than mine, local diesel tech says it happens and no real reason why. Running at cruise control 70 It will get a best of 14.7 and a headwind will knock it down below 14. I dragrace and tow a 42ft enclosed gooseneck hauler(14,000#). Normal mileage is 8.9 towing 67 mph.. Headwind will take it below 8.0 I check all fuel mileage by filling to the neck and useing the trip odo. The truck indicator is usually within .1 to .2 mpg of the actual. This truck has 20,000 miles on it and the fuel mileage has not improved with age as I have towed with it from 500 miles on. The LLY has been a bit of a disappointment. I have owned Chevy trucks all my life and am not about to change but this particular truck is not the best one I have ever owned. My LB7 trucks would get 10 towing the same trailer and have been as high as 11.5 on no wind level ground.

Gary

[LJ]

Hey guys, this is my first post, my first diesel pickup, and so greetings to all.

My truck is a 2005 2500HD w/ Duramax bought 6/1. The first 1,000 miles, the DIC said I got 17.4 overall. When it turned over 1,000, I reset it. Since then, overall, it's been 19.1.

Good points on slowing down above. That Allison tranny won't let me coast. I can see that driving habit changes will help.

[6APPEAL]

Purchased a 2005 Chevy 2500 HD Crewcab Duramax/Allison 2wd on 6/18. Just about ready to fill up my 1st tank and have been getting between 16 and 17 mpg according to the DIC with mostly city driving. I'll manually check that upon filling up to see how close the DIC is. I've been taking it easy, staying under 2500 rpm. Taking a trip this weekend and should be above the 500 mile mark listed in the owners manual, so I'm curious to see what kind of milage I'll get with all highway driving around 70 mph. This is my 1st diesel, which I bought for the towing capabilty. But, I will say it's getting within 1.5 mpg of my old 4.8l C1500 extra cab for the same daily work/home driving. Should exceed the gas burner while towing and not be as hairy to drive.

[6APPEAL]

1st tank of fuel last night. Figured my mileage (361 miles on 19.61 gallons), 18.4 mpg. All I can say is WOW. The DIC was off about 1.5 mpg, but who cares. That is the same mileage I was getting with my 4.8 gas burner in the same driving conditions. I'm interested to see if it get the same on a road trip. The gas burner would get around 23 (70+, air on, unloaded). I know the diesel will blow it out towing.
John

[dieselmaybe]

Just bought a new Chevy 2005 2500HD LT Duramax/Allison yesteday. Had 3 miles on it when I left the dealer. I reset the DIC after driving home, about 25 miles, and checked it with the cruise control set at 60mph, it climbed to 18.5 after about 10 miles. How accurate is the DIC reading? Just curious, I intend to refill the tank and check it the old way this weekend. I test drove the Ford and Dodge and liked the Chevy best. This is a very nice truck. Also, I have noticed a lot of discussion about tire size. The dealer where I bought mine has 265/75s on his demo and said he thinks it lowers the power and fuel economy but shouldn't hurt anything or affect the warranty. I would really like to upgrade these 245s to 265s but don't want to lose much fuel economy, any opinions would be appreciated. (It doesn't seem like a 3.6% increase in diameter should have much effect)

[dieselmaybe]

Checked the unloaded mileage the old way on my new 2005 Chevy D/A. In town, 100 miles 13.8 mpg. 200 mile highway trip Saturday, driving fairly easy 55-65 mph it got exactly 19 mpg. The DIC was fairly accurate also. It was saying 13.5 in town and 19.5 on the highway. I also upgraded to Cooper Discoverer ATR 265-75 E rated tires. I couldn't stand those little 245 tires . Speedometer is off a little, at 60 mph my GPS says 61.2 mph. Before changing the tires the GPS read 59 when the speedo read 60. I'm liking this truck more every time I drive it.

[Bill W]

I have a new 05' extended cab regular bed. with 300 miles on the truck I am getting 14.5 on the city, 21 on cruise control at 60 mph per the display

[VANBC2500HDDA]

I just got a new 2005 Dually Crew SLT 4x4, and so far the trip computer is scaring me, average is 10MPG....

Does the mileage really fall off on the 1 ton trucks?

My last truck was a 2500HD

[cruzar]

I just received my 2005 2500 hd 6600 and took it for a road trip kept it at 65 - 70 and if the computer is correct it was steady at 18.9 and on the ranch with hills and draws in 4 wheel it was at 17.8 I am pleased at this time.