this truck is the first diesel i've ever owned but it is the third 2500h.d. i've owned the other 2 having the 6.0 gasser. i have to say on the fuel economy side of things i'am very dissappointed with the lly. i towed my 24foot enclosed trailer for the first time over the weekend and averaged 8.5 m.p.g. my gassers averaged 8.2 i guess i dont know how everybody else seems to get this great mileage they talk about. the trailer weighed about 6k and i drove 72m.p.h. just food for thought or my 2 cents.

There is definately a problem. Let's hope that GM comes up with a solution.

Sounds like promod's is worse than yours, Max Power. I didn't think mine was bad at all. Anybody willing to do a test? Drive with your trailer three different times, same route, start with full tank, accelerate as close as possible to the same each time. 1st run, stay at 55, 2nd run 60, 3rd run 65 or 70, whatever you want.


Dennis

"I can't drive fifty five." http://www.dieselplace.com/forum/smileys/Embarrased.gif

promod, here is my discussion on the same topic.


http://dieselplace.com/forum/forum_posts.asp?TID=12333


baimpala, I guarantee I could drive 95 mph with my LB7 and get better mileage then my LLY at 65. That should give you a pretty good idea just how much differnce there is. In fact, with my LB7 it really didn't matter how fast you drove. http://dieselplace.com/forum/smileys/Evil%20Smile.gifEdited by: Max Power

Folks, in order to do this correctly, we have to establish "like parameters" to line groups of trucks up for "apple to apple comparison". I will go first:


bone stock engine/air filter/fuel filters etc. 3.73 gears. allison auto. I have a short box with a cap on it. only deviation from stock is the brand of the tires. goodyear ats -vs- the other guy's. now that my truck is fixed (we had a bad selenoid in the turbo, we have a good mechanic at BANNER CHEVROLET in Orrville Ohio) I will start to track my mileage again, the first tanked I checked indicated 21 mpg on MARATHON DIESEL the 2nd 14 (BP) but we had the check engine light starting to appear and the problem was affecting everything.


If we get a thread going that is columnar about the componentry,we could have a valid comparison going and maybe we could see where the issue is. my dad did design work for Goodyear and we knew that if the mileage dropped and the only thing changed was the tires, take em back..........I just said this because tires can kill mileage as well as 4.11 -vs- 3.73's etc.


at least it will be an interesting excercise and be more valid than "I get 28, you get 12, must be something wrong with your truck" :-) (I didn't say I had the sails up, getting a free push......)


have a good one,


dave


2004 100% stock goodyear ats 3.73's truck cap auto

There is a problem here........I have the same mileages!http://www.dieselplace.com/forum/smileys/Angry.gif

forgot to say I am adding sway bars, but those shouldn't change the mileage but does need said

I tested mine with and without the edge. It made no difference. So the edge is out of the question. Other then that, the only other thing that could affect the mileage is the tires. BUT my tires were the same tires that were on my LB7. I actually swapped rims and tires. My LB7 was almost 50% better mileage, so that eliminates my Tires IMO.

I just returned last week from a 1600 mile trip to Hatteras Island towing a 30+' trailer that weighs approx. 8,000 lbs. We averaged 9.5 on the DIC, which I felt was decent for a truck that only had 3200 miles on it when we left. The DIC was reset when I pulled out of my driveway, as well as when we departed Camp Hatteras. We got about 19.5 without the camper driving around the Outer Banks. This weekend's trip to Berlin Lake averaged 9.9 towing. I live in mountainous southwestern Pennsylvania, and tow about 65-75 mph, depending on the traffic, weather, etc. I'm satisfied with the fuel mileage towing, and impressed with it unladen. My previous four trucks were all gassers, so I can't compare apples to apples. It's definitely stronger towing the hills, though.

this truck is the first diesel i've ever owned but it is the third 2500h.d. i've owned the other 2 having the 6.0 gasser. i have to say on the fuel economy side of things i'am very dissappointed with the lly. i towed my 24foot enclosed trailer for the first time over the weekend and averaged 8.5 m.p.g. my gassers averaged 8.2 i guess i dont know how everybody else seems to get this great mileage they talk about. the trailer weighed about 6k and i drove 72m.p.h. just food for thought or my 2 cents.


I tow a VERY similar setup to yours and just got back from a 1000 mile trip. The only difference is I have a 3500DRW but I averaged 10.1 MPG. My truck seems to get better mileage when I'm driving faster for some odd reason....but I like to average 70-80. The same trailer and load netted me 6MPG on my former 6.0L Denali XL.

[QUOTE=promod]....but I like to average 70-80. The same trailer and load netted me 6MPG on my former 6.0L Denali XL.





Where can you average 70-80 MPH?http://www.dieselplace.com/forum/smileys/Ermm.gif

Can't say loaded yet, but solo my bet has been 19.5. Going to Montana and back he average was 17.5. Economy reall goes down quick when getting over 72 mph. At 80 in the western mountains I got 15. I now have 6400 miles on it and around town its getting better. This is still better than the 6.5TD ever got.





Greg

My mileage is similar to Promod's, all averages are hand calculated and corrected for 265 tires, include TTS cat back, Amsoil air filter, Amsoil lube bumper to bumper, Access Tonneau cover.


Max unloaded mileage = 16.81mpg, Quad level 2, -CAT, beginning odometer = 7136 mi.

Min unloaded mileage = 12.03mpg, no power adder, beginning odometer = 4558 mi.

Towing - 13450lb GVW, Quad box on level 1, 70-80mph w/ cruise control, 1605 total miles. Beginning odometer = 5106 mi.

Best tank towing = 11.56mpg
Worst tank towing = 8.5mpg
Ave towing = 9.94

This is my second Duramax, my first was an 02 3500, D/A, CC, 4x4. Mileage unloaded is similar however towing a trailer the 02 was better.
Edited by: RaceHemi

i did forget to post the m.p.g. i get empty it's about 14.6 and i don't think thats very good.

Melvin:

Out west there are some pretty high speed limits, much higher than our wimpy East Coast 65 mph. If you get a US Road atlas with a summary of state by state traffic laws, you will see what I mean.

I have another tid bit to throw in here.

All MPG DIC based though I hand checked it several times and it has been +/- 1/2 MPG

I put 6000 miles on my truck before I towed for the first time. (long break in) I was getting 18.5 city and 20-22 highway, Truck is totally stock drivetrain.

My trailer weighs ~18,000. I was getting about 9.8-10 dragging it around city/hwy.

After towing that load the truck is getting 16.5 city and 18.5 highway! Odd. Could it be some sort of adapt in the tranny or engine?

04 with 3.73 allison 4dr 4wdr mileage has climbed from new10.0 mpg w/ 22' trailer to 13.5 14 hwy to 18.5 now have 11k .recent trip to canada 18.3 loaded passengers and gear plus auxilary tank. trip to south dakota 2 persons all our stuff and xtra fuel 18.7 have been impressed so far have some minor service. (water pump) noise sounded like squeaky belt.

This is a touchy subject with me. I jusy bought a 2500 HD 4x4 LLY for three main reasons. Fuel economy the quietness of the engine, and the allison tranny. Well the engine noise and tranny are great but my fuel economy sucks. Worst is 13.2 not pulling and the best has been 14.6 mpg. It is getting better sloooowly. I have not pulled a trailer yet. I only have 2400 miles on the truck will it get any better? I opted to buy this truck instead of another Ford (did I say the F word?) but I get 17-18 mpg consistantly with that other truck.

I have a 24ft travil trailer towed Great. My old truck would get 7or 8 mpg this truck got 12to 13 mpg towed with it 2 times now and love it!http://www.dieselplace.com/forum/smileys/Big Smile.gif

Filled up this morning. Had no loads with this tank, just city/highway.. about 50/50.. 20.212 Gallons 401.2Mi Avg 19.8 mpg.

Stock truck except for Edge, I run around on level 3 all day in tow/haul. 1/2 stop and go traffic, half 80mph on the highway. I average 15.5 mpg. But I stomp on it every chance I get.

I had a 2003 LB7 and with hypertech and found mileage pulling a 7000 pound trailer to be 12.5mpg with the speedo adjusted for 285's. I now have a LLY with 20,000 miles on it and towing I get 9.9mpg with no tire adjustment. Unloaded with the LB7 I would get 18.5 to 19mpg. The new truck gets 15.8 at best. I am not happy either. Has anybody found that a change from the stock air filter system has made any changes in mileage? I also have light blue smoke once and a while after hours of idling at a job site. Does this sound familiar to anyone. The shop checked the injectors on the computer and found them to be within spec. Any feed back would be greatly appreciated.

sorry posted this reply on the wrong forum. Should be under mileage.

I think anytime you increase power and torque you are going to lose some mpg. That is why you are seeing a difference between the LB7 and LLY mpg's.

I think anytime you increase power and torque you are going to lose some mpg. That is why you are seeing a difference between the LB7 and LLY mpg's.


I disagree. My LB7 was over 400hp and had NO PROBLEM getting 20mpg+ solo and 14mpg+ pulling.

That is one of the great things about diesels. With a given displacement, almost anything you do to increase max power (no pun) does not take away from the economy of the engine. If anything, it will increase the economy.

After upgrading the power, drops in fuel economy can almost always be traced back to the right foot....

I also had an LLY that is getting poor fuel economy. EDGE TO THE RESCUE!!!


Before box empty avg 14


after-----------------17


Before box loaded avg 8


after-----------------12


This is on the lowest setting. TRY IT!! YOU'LL LIKE IT!!

Melvin:
Out west there are some pretty high speed limits, much higher than our wimpy East Coast 65 mph. If you get a US Road atlas with a summary of state by state traffic laws, you will see what I mean.


k1xv:


Regardless of where you drive. Do you have any idea how fast and how far one would have to drive, to average 70-80 mph?http://www.dieselplace.com/forum/smileys/Geek.gif

My edge is on the way. Can't wait. Hopefully I will see the mileage increase like yours. It has taken a while for the edge to get to Canada - at least in the west. I put on about 6,000 miles every month so any increase in mileage is money in my pocket. Old LB7 without chip had way more power of the line than the LLY. Anybody else feel the same way? Just finishing the fabrication of a pre-runner bar this weekend. Looked around in all the magazines but couldn't find any for the GMC so I decided to make my own with a tube bender. Wasn't very hard. Didn't want my truck to look like everybody else'e. Three Hella 4000 Ralleye lights should help out. Does anybody else have any cool light bars on their trucks?

My 2500 HD 4x4 on 315 tires now w/3000mi. on it avg 15.1 mpg on a 1200 mi camping vacation loaded w/camping gear and no trailer. Lots of I-5 @70 to 80 mph. My brothers http://www.dieselplace.com/forum/smileys/Throw Up.gif ' 02' F--- F350 on 285 tires powerstroke got 12.5mpg on the same trip filling w/me and hand checking our mileage together, although he had a pop-up camper on his truck so I did expect his mpg to be worse. "I Hoped".


Best I've ever been able to get has been 17.6 @ 55-60 driving it like my mom would on flat HWY 126 to Ventura & back. Seems that anything above that it just gets worse. I'd say about 16mpg on the fwy empty @ 65-70 seems about the norm for me and about 12.5mpg city driving here in Saugus.http://www.dieselplace.com/forum/smileys/Thumbs Up.gif


My mileage is not what I expected reading about all the guys posting 18-19mpg. But still not bad for a big heavy truck. It beats my old 2wd '92' 454 dually on the same camping trip by 2mpg easy and more power TOO!!!

I only have 2900 miles on my truck (got it last week) but i average 19-20 mpg empty and 12-13 mpg with 8000# trailer and four adults in the cab. I try to stay at or below 70 mph.


my first few tanks were running empty to and from Maine, averaged 20.3 mpg on the way up doing between 55 and 70 and a constant 70 mph on the way back yielded 19.1 mpg.


gary








gary

I have 2 of the LLY's. The mileage is definately not there. I think the emmisions change did it. I have heard from other drivers all the big 3 took a dive this year in fuel mileage. The rumor is the 05 will do bad also. GM did not have time to work the bugs out in the 1/2 year of the LLY.

I just filled up and got 17.5 on the DIC and 16.5 hand calculated driving in the city( although the city is Boise). Last week towing a 21' camp trailer and loaded with gear through the mountains I got 14.2mpg. I've talked to a couple of people with LLY's and there seems to be two different trucks out there. Theres the 12-13mpg group and then theres the 16-17mpg group. My truck is stock except for the max mod. I wonder if manufacture date makes a difference. Mine was built in June. I feel for you guys getting the poor economy.


Rob

2005 Chevrolet 2500 HD Crew Cab 4x4 Duramax LT Bone Stock picked up 8/24/2004 - first tank averaged 17.7 mpg based on DIC and 17.8 mpg calculating by hand. Combined driving 50% stop & go traffic & 50% hwy running ~ 74 mph. This truck is awesome!!!http://www.dieselplace.com/forum/smileys/Approve.gif

i picked my truck up yesterday put 280 miles on it got 19.5 mpg on the DIC and 18 mpg calculating by hand.


was built in June at the Pontiac Mich. plant.

My truck was built in March 04, and our roads are up & down, not a lot of flat roads. And with the lift and 35" tires I did expect to loose a little mpg. I do still LOVE my Chevy Truck. This thing is BAD to the BONE!!! http://www.dieselplace.com/forum/smileys/Rock On.gif Edited by: h8s4ds

I know it is on here somewhere but how do i hand calculate the mileage with 265s on mine? Isnt it like multiply miles by 3.9 % or something?

I'm not sure about your 265's but my 315's put my speedo off 14%, so I add 14% to my odometer reading and divide by gallons used.http://www.dieselplace.com/forum/smileys/Rock On.gif

I have 1900 miles on my GMC and pulled an old pickup on a car trailer last week (not very aerodynamic) over 700 miles through the appalachians. The trailer was approx. 7000# and I hand calculated 12.2 M.P.G. not taking into account I'm running 285's and my speedo is 3 mile an hour slow.

I just got back from a vacation from MN to Las Vegas and back. We put on 3725 miles with a best tank 21 mpg and the worst tank 15.6 mpg. We did a lot of mountain driving in New Mexico, Utah and Colorado and city driving in Las Vegas and Lake Havasu City. My total average for the trip was 18.4 mpg with an average speed of 54 mph. I now have 4500 miles on the truck and just love it. I had a 2003 5.3 prior and hated that, it would not have gotten up the mountains without runing 4-5,000 rpms. The new one didn't shift down once. I've come to the conclusion 65 mph will get you 20-21 mpg and 75 mph will get you 17-18 mpg and anything faster really drops off. It should have one more gear as it has plenty of power but I am very pleased with the whole truck.http://www.dieselplace.com/forum/smileys/Clap.gif

Its really hard to compare MPG, with factors like driving conditions, terrain, tires, driving style, altitude, humidity.


I see 13- 14 mpg towing my boat 3500#. Compared to 11.5 -12 on my 6.0 GM Gas


Unloaded i have seen 15.5 to 19mpg. 17.5-18 seems to be my average tank. As with all trucks i have owned, when i do the quick trips, stop and go, or I'm in a rush my mileage is adversly affected

I work at a GMC Dealership- last week we had an '04 2500HD come in with 18.7mpg on the DIC.


My '05 2500HD C/C (stock) has averaged about 16mpg in the first three tankfulls- a little towing, a bit of hossin' the throttle, and a whole lot of driving too fast (in Atlanta, the average hwy speed is 70-80). I could get it higher if I would behave.http://www.dieselplace.com/forum/smileys/Evil Smile.gif


I'll be towing a 4500lb camper this weekend- I'll let you know the results.

I did a mpg test on Sunday. Drove 235 miles round trip with the cruise control set at 70 mph the entire time as traffic permitted. Filled up with 11.6 gallons for an average of 20.2 mpg. Not bad imho.http://www.dieselplace.com/forum/smileys/Big Smile.gif

i drove a brand new (11 miles) 05 CC SB DA 4x4 2500hd today and got 18.1 mpg

18,000 miles on the truck and things seem to be getting better. The last tank (unloaded) was 21.4mpg with avg 48mph per DIC. Highest I've gotten yet on a tank.

I picked up a new 04 2500 4x4 yesterday, and drove the 170 miles home. According to the DIC, I got 18.9 mostly freeway, mostly uphill. Traveled the same route two weeks ago with my 03 8.1 2500 4x4 and got 11.2. Hopefully I got a good one..sorry to hear of the disappointment some people have.

17 mpg at 72/73 mph on I-80 between Elko and ParkCity. 3,000 miles on unit. About the same running around town. This was off the DIC. Hand calculations indicate about .3 mpg better. Old 8.1 would get 13 mpg on same run.

19+ MPG on a 60 mile trip mostly on I-95 yesterday. Averaging around 16-17 MPG in stop and go traffic around the town. 1900 miles on the truck. On a major 600 mile trip in early august the average was 21.6 MPG. Only towed 144 miles to date and that was stop and go break-in speeds and averaged 11.7 MPG. All readings from the DIC.

Now over 10K miles on the truck. Went to JK's and back this weekend and it was 1025 round trip and got 19.2 mpg. On the way back I was running a study 75 mph and on the way up it was anything but steady speed. I think the mpg is great, but I am use to my .5 that only got 16 on a good day.





Greg

My LLY has 2000 miles on it now, picked it up in July. Best mileage so far has been 20.8 on a 240 mile trip empty. Just pulled a 2500 Lb trailer loaded with ATVs on a 225 mile round trip averaged 16.7 All around average has been 18.1 I really expected better for my first diesel but I can say I am terribly disapointed. I enjoy the extra power. I had a Ford F150 4x4 with a 4.6 It was a real dog for power but I got decent mileage.http://dieselplace.com/forum/smileys/Big%20Smile.gif

Just to throw this in here.


I have crew cab with 6" lift 35" tires.


When I drive normal best I can tell Im sitting around 15mpg on the freeway and 12 in town.


The last trip I took to oregon I crosses 330 miles in about 3.75hrs. Thats from Sacramento to Medford, half flat, half hills, all fast. On that trip I sucked down 26 gallons of diesel wich is still almost 13mpg.


So the mpg is ok, but before I got this guy I had an 03 extended cab. I took it on a trip from Sacramento to Vegas and did my darnest to stay at 90mph. Had to slow down occasionally, but I wasnt making it a pleasure cruise. I basicaly got 20mpg doing that, but that was a stock truck with edge added. Im thinking of changing the gears in the new and seeing what happens.

Well, I'm not sure what people expect for mileage out of a big pickup? I always thought 18mpg out of a CC 4X4 was outstanding, I guess it's perspective. My V6 Toyota 4X4 got about 18-18.5 back and forth to work. With the "Big Pickup" I get 18.2-18.7 consistently, this is some in town 25-30% and 25mi of two lane road with a town to go through about halfway. Drive 60-70mph. Last 3 tanks mpg's are edging up ~18.9-19. I have 7200mi on her now

My lly now has 17000 miles on it and i've seen mileage consistantly 15% worse than my 1997 F350 powerstroke with 4:10 gears. Actually I did two 3500 mile trips. One with the 97 powerstroke pulling a 20 foot cargo trailer and all of my family's belongings. Piano, cast iron compressor millions of books etc. We would get 12 mpg if I stayed at 60 mph. The same trip with the 04 2500 Duramax alison 3:73 gears with no trailer but a cargo bed full of furniture including an antique bed headboard square to the wind got 12 mpg also. Same speed.





Lets see, Ford and trailer weighing in @ 18000 pounds gets 12mpg.


Chevy at "about 9000 pounds at most, no trailer gets 12 mpg.


Why did I sell the Ford?


Does anyone know if we are all just complaining to eachother to no avail? Does Chevy acknowlege that there is a problem?


My dealer says that all is okey dokey with the truck. GM failer to e mail or call back after promising to do so. " I guess we wrote down both your e mail and phone number wrong"


Funny thing is that the service consultant drives almost the same route as I do with the same truck with the pre LLY engine and gets 20-22 mpg. Somtimes better. If I drove at the speeds he drives at I'd get 15 mpg.


So, he is passing me @ 75 mphhttp://www.dieselplace.com/forum/smileys/Big Smile.gif every morning getting 20-22 mpg while I'm literally in the slow lane doing 60 mph trying to squeak out 18 mpghttp://www.dieselplace.com/forum/smileys/Confused.gif.

latest info on mileage, now have 15k miles here is how the truck is setup , amsoil 5-30 hd diesel oil, amsoil oil filter, amsoil air filter last trip to canada 2100 mile round trip full load w/extra fuel tank and all our gear 4 passengers worst mileage 18.9 best out of canada into minnesota no air on 50-60 degree temps 22.1 mpg. this one is running better after the air filter install. the more i drive it the better it runs ,we have a 2000 ext long bed 4x4 and the 2 trucks are almost identical in performance .approx 70% of my driving is towing 14'-27' enclosed trailers avg. 12.5 to 14 towing. mileage is calculated on fillups and not taken from the dash reading, this gives an average not actual mileage at that time.

occitiger, I have a six inch lift and run 35's too. I get 16-17 mpg on the highway at about 70. i get this number from resetting my business trip calc. I know that my speedo is off so recalculated it is about 19+ mpg with the tires. In town I get 12-15(unadjusted).

Blowinsmoke,


70???????? Man thats to damn slow. I got spoiled with my 03 becuase speed was not something that it concerned itself with. At 70 mph in that truck Id run around 22-23 mpg. Which was better mileage than my motorcycle, of course Im heavy, drive fast, and it was a small bike, but thats beside the point. Do you have anything else besides the edge/***, and intake going on with the powerplant part of your truck. I really want to get this cat. off of my truck, but when the dealership installed the exhuast kit they cut and welded so I need a torch and mig to get the big free flowing down pipe on it. I also need to order that EGR plate, unplugged my truck runs better. All things considered I have been a little dissapointed in buying the 04, however it was a kick ass deal and an upgrade from LS to LT and from extended cab to crew cab. Plus, its way better performance and mileage than that 8.1 ltre gasser.


The grass is alway dead on the other side...

I was getting 18.8, put a cab height cap milage went too 20.6 http://www.dieselplace.com/forum/smileys/Big Smile.gif lly is completely stock with 2400 miles I towed single axle trailer with harley road king to cherokee nc, lots of mountains, dic showed 15.9, 16.2. I have been considering Edge/juice, I don't need more power at present. has anyone improved fuel milage with Edge/juice?

I can only get 16-17 mpg on a 1000 mile trip to MN this last weekend that is with the ac for half the way. I was getting 17-18 with stock tires and that was with only 1000 miles on the pickup. I have 264/75 BF AT KO tires on now. And yes I did convert for the bigger tires. Are you guys running stock or what for tires and do you have the and open tailgate or cover on the bed?

I saw an increase on my LB7 and LLY with the edge. I'm sure you will really like the edge ***. It is so good it should come standard.Edited by: blowinsmoke

I was getting 18.8, put a cab height cap milage went too 20.6 http://www.dieselplace.com/forum/smileys/Big Smile.gif lly is completely stock with 2400 miles I towed single axle trailer with harley road king to cherokee nc, lots of mountains, dic showed 15.9, 16.2. I have been considering Edge/juice, I don't need more power at present. has anyone improved fuel milage with Edge/juice? I got an increase on my 3 LB7's both towing and mt. I have 2 LLY's and both dropped 1-3 mpg with the Juice, except for towing very heavy. And this is driving easy. I have installed a 4" exhaust on one of them today and I am hoping for a mileage increase.

With juice setting "1 millage", towing jetskis I get 14.75 MPG without juice towing the very same trailer I get 15.5 MPGhttp://www.dieselplace.com/forum/smileys/Geek.gif

<DIV>04.5 LLY cc, sb. Made a trip this weekend 700 miles round trip. Four wheeler in the back and towing a 1200 lb. trailer. 75 to 85 the whole way and got 9.5 on the DIC. My LB7 would have got at least 14.5 to 15.5. Has it been confirmed that the newer LLY's are doing better? Mine was built in Feb.</DIV>

Mine was built in Feb. and is getting about 14.4 city, 20.5 highway(under 70), and 10 to 11 towing a tall 10K lb. 5th wheel.


I don't think that is too bad at all seeing that I have 285s on it, and have cranked up the T bars.


The problem with mileage is how I drive sometimes. All of those numbers can go out the window really fast if my foot gets heavy! http://www.dieselplace.com/forum/smileys/HiHi.gif

pulling my open cal hauler with a 3100 pound car on it so 4500 pounds car and trailer I was getting 17.2 MPG looking at the DIC. now thats doing around 65 MPH. I've seen 21 MPG on the highway doing about 70. the truck is bone stock with about 4200 miles on her.

Mileage threads are always more amusing than fishing stories.

Can't say about the LB7, never owned one.

My LLY mileage tale goes like this:

13.5 during the work week. Wife driving, but it is a really short distance (3 miles round trip) many lights so the truck never gets up to speed. Understandable, getting 7000 or so pounds moving from a stop again and again isn't gonna be free.

19.8 best ever babying it with 65 cruise on open flat freeway.

11.7 worst ever towing, the boat in the pic, and wasn't being nice to the truck at all, running 85mph a LOT, stomping down from every stop, and hammering down to pass whatever wasn't in as much hurry as I was. If 75% of that tank hadn't been on the highway (even though I was running 85 to 90 there) I bet it would have been 10mpg or worse.

14.7 best ever towing a two horse with two large halter horses in in. This was a 70mph cruise the whole way about 160 miles, first half all flat second half was hilly, average was 14.9 into the hills but the second half dragged it down.

I have found that 65 to 70 is a speed the stock truck really likes. There is a small penalty for bumping up to 70 and a little bigger penalty for 75, past that you really start to pay dearly. When its all said and done I can easily average 18.3 to 18.5 on the freeway (not trying to get best mileage, but not doing things to kill it either, just driving the truck) and 14.5 even 15 in realistic city traffic driving that allows speeds at least 40 to 45mph (not like wifey who gets to 20 or 30 for a sec then back to stop repeatedly in her 5 minute trek to work)

I have one of the first LLY's. It was built in January and I was extremely disappointed in the mileage. Towing 5000 pounds, it was 10-11 mpg; all around driving was 14 mpg. I had read threads that stated the mileage increases greatly after 10,000. Well, I just rolled past 15,000 and I am very happy to see that my mileage has increased to 17mpg empty. http://www.dieselplace.com/forum/smileys/Clap.gif I have not towed for a couple of months. I have tried to watch the lead foot, but maybe there is some truth that these engines get better with age. I also changed the fuel filter today. Maybe that will help it as well.


My truck has a 1" torsion crank and 265 tires. I adjusted 3% to offset the larger tires.

Here's my $0.02:


I have a 2500 HD D/A LLY. Has 2800 miles on it. Bone stock except for AFE St2 and Racor pre OEM fuel filter. Truck has the 245's on it.


I have not seen ANYTHING better than 13 MPG, unloaded, not towing anything. No smoke, no rough idle, no overheating (but Im not towing up a huge hill with my 10k boat either) but once in a while, seems to run rough.


Im going to see if I can get this reflashed this week to see if that will help. I'll keep you posted.

re lly fuel milage-i have a 04 3500 4x4 cc dually-ally trans and lt235/85r16 tires (31").i carry a 10.8 corsair camper loaded.truck is covered with stuff-total weight is 12000 lbs wet with the wife and i. i have a afe stage 2 air filter system (part#54-10612) and a hypertech power programmer (part#30029) set on 70 hp. my average fuel milage is 14.75 mpg canadian.this is over a 2000 mile trip! hills-flatland and-towns-cities-etc etc stop-go etc etc!my max speed is 70 mph-my avg speed on the highway is 60 mph! not real fast but not slow! i use the cruise control all the time on the highway.the power programmer and the air filter made a big diff in power and in mileage.i gained 3 mpg with this 2 add ons. next is a mbrp cool dual exh system with the replacement head pipe.cat is going to the back of the garage! with thesehttp://www.dieselplace.com/forum/smileys/Big Smile.gif mods it will now be as good as my 2002 lb7 with the same mods but not better! see ya!