Just returned from a 500 mile round camping trip and averged 9 mpg, pulling a loaded camper at about 6500 pds. Front tires have 60 psi and the rears are at 80 psi. Used tow-haul and did not lock out the OD. I expected better mileage.



We are leaving on a trip to the Florida panhandle next week and was hoping to get better mileage. Camping is the main reason we bought the diesel.


I had read many threads touting the LB7 as having high teens for overall mileage. Still can't get this puppy above 14.5 mpg. Sure, driving habits and conditions will vary, but most of my driving is highway.


Could the EGR and/or the CAT cause the LLY to drop mpg? Will chipping the engine help when chips are available? Maybe near 10,000 miles she will finally break-in and improve...

The worst mileage I got with no load was 16mpg and that was driving hard (85 hwy and stomping on it from almost every stop). I usually drive 80% hwy and I'm averaging 16mpg to 17mpg going 70-75 on the hwy with no load. I've gotten as high as 19mpg. These numbers are all combined hwy and city driving numbers. My truck is 100% stock.


I know this isn't an answer to your problem but it can give you a reference on what you might expect if you find the problem. Also this is using California fuel http://www.dieselplace.com/forum/smileys/Disapprove.gifwhich sux and is over priced.http://www.dieselplace.com/forum/smileys/Angry.gif


Good luck.

Most LLY's aren't able to break 14.5 unloaded that I have been around. The only six speed truck I have seen does get much better though.

I forgot to add that all my mileage calculations are manually calculated. The DIC on my truck is not very accurate for obtaining the fuel mileage.

I've logged every tank on my LLY and when stock I got an average of 15.5 Most of my driving is in the city. Since adding the catback exhaust and programming the average is 16.22 under the same conditions. Mileage is figured by hand as the DIC isn't very good in my book. Truck has about 4500 miles on it.


McRat has the same programming in his truck and just got 11.1 towing at 16,000 lbs combined I believe. You can see his comments under this thread First Impression - TTS tune for LLY Engines (http://dieselplace.com/forum/forum_posts.asp?TID=9038&PN=1)Edited by: Diesel Tech

I have 5000 miles on my LLY. Drive about 7 miles to work (one way) and have to climb a 3/4 mile long hill before the truck is even warmed up. I'm still averaging 16+ mpg. On the hwy (if I keep it around 60mph) I'm getting 19-20mpg. At speeds around 70-75 on a 300 mile run I'm getting 16-17. All of these numbers are empty, not towing.


I just towed 7500lbs and averaged 13.5. Had towed 13000lbs for about 100 miles (stop and go, some hwy, several long hills) and averaged 11mpg. My DIC is very accurate. I have noticed that the mileage seems to be going up after I have been towing some heavy loads.


Norm

I avg. 18.1 (12000 + mi)up hill, down hill, flat, city or hwy with the air or without. Avg mph is 46.3 I never carry anything. I had a 5.7 Hemi before before this Max the best it ever did was 13.5 so I am digging this 18.1 with diesel at $1.55 and gas at $1.94http://www.dieselplace.com/forum/smileys/Big Smile.gif Edited by: ntnbolt1

Well living in Dallas I'd say 95% of my driving is short trips less than 5-6 miles with lights every 3/4 to 1 mile. All stop and go all commuter type traffic. In the 1700 or so miles I have my average is 15 MPG city only. I calculate by hand with a great little spreadsheet that I got off another forum. I havent had many highway trips yet, but the short ones I have had have been great mileage. Heck with 15 I am happy as a lark. My old F350 never once broke 13.5 city or highway.

Anyone think the height of the camper and the additional drag could be the difference?

I towed a ~8000lb race trailer/car/spares with our 7120lb 4x4 3500 SRW, with 4 people and some other stuff. About 16k combined give or take 200lb. It is a dura/ally LLY with no mods other than a TTS Tow tune.


Measured mileage for the round trip was 11.1mpg, DIC was 12.2. Lot's of stop and go (Vegas Traffic), temps in the upper 90's, altitudes from 4000' feet to 1000'. Most cruising at 65-70, with jaunts up to 90.


My E-350 with 7,000lb (14,000'ish) did a best of 7mpg on the same trip. So I'm happy. That's about 50% better mileage with more weight at higher speeds.


Sure the DIC said 15-17 in some stretches at 60 mph, but from door-to-door it was much lower. If you don't have to decel/accel or go uphill, your mileage will be great.

Sonny, did u try running w/ T/H off on the highway?


I rarely run T/H even pulling 13-15k loads.

I thought about not using the tow haul mode, but I figured the different shift point changes for the tranny would make it easier and safer to tow. This was my first tow with her. I might try it without the tow haul and see if there is any difference. Although, using it sure was nice on speeding up and slowing down. I am completely at odds on why the mileage is so bad. My speed averaged 65 mph. The truck runs fine. I am debating on taking it to the shop before Florida. Maybe there is a undiagnosed probelm.

I know this is about LLY (2004.5) but here is a picture of my mileage chart form my 2002 LB7. As you can see I keep track of pretty much everything. It looks like the LLY engines are like the new Cummins 600 when it comes to low fuel mileage. Sorry to hear about the low MPGhttp://www.dieselplace.com/forum/uploads/mileage_pic.JPG

Ya want something off the wall, I have a 32' 10,000 lbs camping trailer that I am averaging about 11.3 mpg at 68-70 mph; I am also pulling a 8,000 lb 28' Haulmark race trailer and the best I can get pulling that has been about 10.5 mpg at 68-70 mph; guess the D/A just absolutely loves working harder!http://www.dieselplace.com/forum/smileys/Clap.gif Oh, and at the moment I only have about 7600 miles, still waiting for it to get better at 10-15000 miles!

Another mileage comparison: Last weekend I celebrated having my D/A for two months by hooking up the camper and hitting the Interstate to see what would happen. My camper is a 31' Hi-Lo and loaded I think I am in the 6700# range. Started out on cruise at 65 and T/H. Got passed so much thought it had slipped into neuteral. Kicked it up to 70. Still got passed but now I'm catching up to semi's; gotta pass'em! http://www.dieselplace.com/forum/smileys/Big Smile.gif Run up to 80 / 85 with one little hiccup. If I just step on it while still on cruise, the truck seem to argue with me about going faster. Kick off the cruise first then step on it, we be flyin' in no time. http://www.dieselplace.com/forum/smileys/Evil Smile.gif Daily drive to work is 60 miles round trip, been averaging 17.9 to 18.3 MPG on a two lane highway. TWS_ANDREW asked if the height of the camper made a difference. I think so, my Hi-Lo is lower than the truck when pulling and even with the 80/85 MPH burst I still averaged 14.1 on that one tank full. After having a gasser all these years, this is a lot better than I hoped for. Can't wait for the 10k miles to see if it gets better on the MPG. The only problem so far is what I stated in another post; severe leg cramps and bruising from kicking myself in the butt for not getting one of these D/A sooner.http://www.dieselplace.com/forum/smileys/Wink.gif

Am I the only one who has heard that trailer tires aren't rated for speeds over 65 MPH?http://www.dieselplace.com/forum/smileys/Confused.gif

Will be towing next week. 26 foot Weekend Warrior. About 8300# loaded. Will be headed down I-5 from Seattle/Tacoma area to southern Oregon coast. Will report back what Im getting.


Im getting 17.4 by hand right now, which is .3 off of what the DIC sez. This is in the lovely stop and go metro area traffic. Im hoping to get 15-16mpg driving 60-65 with the trailer.

SonnyBear,


I noticed that you are running 265's. Are you correcting for the difference in tire size. If not you are calculating at a 3.9% error. Take your miles driven and multiply by 1.039, then divide by gals used. That sould give you correct mileage.


Ex.
Say you show 330 miles on odo...Multiply by 1.039 to get 342.87 then divide by gals.


Hopefully that is your problem. For what its worth, I have an early 04 LB7 and the best I have gotten so far is about 18MPG. The lowest I have gotten is 11. That was towing 6k through the mountains. I average about 12 to 13 in mixed. I have 5k on truck so far. I am also running BFG 285's. I am sure if I went back to stock and drove under 60 I could get 18-20mpg, but what fun is that?


BillEdited by: Redapple

Good point on the speedo. When the dealer recalibrated the ABS, I was told that the speedo/odo was also recalibrated for 265s. I have read varied opinions on IF the dealer can reset the speedo or not. I will try the calcs of 3.9% and see what I get.

Paper, what do u mean 65mph trailer tires?


I run the same tires on my trailer as my truck, wear them down to 1/3 tread left then put on trailer.


Don't forget about the U-haul trailers and the 45mph speed limit, had one pass me on the turnpike behind an Exploder and I was running 78mph http://www.dieselplace.com/forum/smileys/Geek.gif

I've had mine for almost two months now and never reset mileage on the DIC, at 7,000 miles my average is 16.6, thats every kind of driving. Two trips I've done I hand calculated at 15.5, this is with 600lbs in bed and cruise control at 75 most of the 620 miles. Fuel around here is still 30 cents cheaper than gas.

Dmax Tim, on the 65 MPH and trailer tires. I recall reading that ST (trailer) tires were only rated to 65 MPH. I'll look around and see if I can find that again.


I wish I could use truck tires on my FW. Unfortunately I cannot get the correct size with a decent load range. Trailer tires seem to always be "on the edge" of being overloaded. Actually, if I loaded my FW to its GVWR it would probably exceeds the tire capacity! But I don't, I'm about or more 1000 under that.


I sure seem to get better mileage towing at 58-60, at least with my prior truck, a 6 L Chevy 2500 with AT and 4.1 rear. I got 10 MPG which I thought was fine.


I now have 270 miles on the new diesel and filled it up today - mileage was 14.5 but that's been all to/from work which is only 6 miles from my house. I hope to get it on the highway soon and run the miles up to 500. I plan to tow my FW over Memorial Day weekend. Looking forward to seeing how it does. It's going to be difficult to keep the speed down so low for ANOTHER 500 miles - The manual recommends NMT 50 MPH! http://www.dieselplace.com/forum/smileys/Cry.gif

I pull my tripple axle snowmobile trailer with crusie set at 82-83mph sometimes faster depends what part of the country I'm in and never had a trailer tire problem. I lube my bearings before every trip though.

Drove approx 740 miles. Averaged 9.8 MPG with the TH engaged.


I-5 @ 65MPH typically towing a 26' Weekend Warrior trailer weighed 8300# going down and 7900# coming back.


Tried some 50 mile stretches with TH engaged and disengaged and either way mileage was the same avg. Did prefer with TH engaged as the truck seemed more sensitive to load and would downshift easier/sooner.

Also noted that my fuel mileage has increased after towing....seems she broke in a tad more and I have more power and better mileage!!!! http://www.dieselplace.com/forum/smileys/Big Smile.gif

I hand calculated to compare with the DIC and the DIC seems to be right on. I am getting 18.5 MPG combined driving unloaded. I towed a 3000# trailer to the coast this weekend and got 16.5 MPGhttp://www.dieselplace.com/forum/smileys/Approve.gif, I did not use tow/haul mode.

First tank of diesel I used while doing the break in (under 500 towing miles, speedy varied 45-50 MPH) was hand calculated at 12.2 MPG. That was 80% towing on the highway, 20% towing on rural roads with lots of shifts, acceleration, etc.


I am pretty pleased with that, but I think I'll go nuts until I get another 200 towing miles and can bring the speed up to 60 MPH at least!http://www.dieselplace.com/forum/smileys/Cry.gif

Reprogramming the tire size in the ABS does nothing for your speedo, and according to GM TAC does nothing at all......GM does not authorize any tire size mods to the duramax....just check yesturday...


speedo operation comes from the output shaft speed sensor on the allison rear trans module. the Allison is comprised of three modules


front, center/body,rear.

It is my experience that brand new trucks that are driven long distances, rather than many short hauls, take more miles to break in. My last 3 new trucks took around 25K miles before their mileage came up, my '03 Sierra is the same. My first 15K miles only provided 14mpg at best. It kinda stuck on that number until about 22K miles then it creeped up to a current average between 19 and 21 mpg driving 75mph unloaded. I now have 30K on the odometer. That’s my two cents worth of experience! http://www.dieselplace.com/forum/smileys/Geek.gif

Thought I would chime in on some "light" towing mpg. Truck loaded with the family, 4000 # p/u camper and pulling 4000# boat, my trip average was 12.5. This was at 55-60 mph, stopping and/or slowing down at several towns for a total of 200 miles (100 miles each way).


Not setting any records, but better than I could get with my 6.0 or 5.7 gasser...


picture of the rig is at the web link in my sig.

I have not towed yet, next weekend I pick up the TH. Getting between 16 and 18 around town. and between 20 and 24 on the hiway. THis is all hand figured and is about .1 off from the DIC. IT only has 2600 miles so far, I am hoping it will only get better.

20-24 on the highway? damn! are you driving 50 mph in 5th gear or something?

i know our LB7 only got a best of 18.5 mpg on flat land without the programer.

I just traded a 2000 F350 for a 2004 3500 SRW. My old truck would get about 10 - 11 mpg with my 12K 5th wheel. So far I have only put about 900 miles on the new truck. At 502 miles ( break in before towing ) I was getting about 14.6 unloaded. My one trip loaded ended up with a 9.6 mpg. I know that it should improve as it goes, so I feel that I will end up with a better number than the ford.


By the way, I was a die hard power stroker. I only switched from fear of the 4R100 tranny. I had the ford modified with the banks stinger but after I have pulled with the duramax, there is no comparision. Chevy does not seem to labor to get the same results.


White is fading from knuckles.http://www.dieselplace.com/forum/smileys/Approve.gif

Just got back from a 3200 mile trip from Washington State to Las Vegas Nevada and back. NO PROBLEMS AT ALL. Total fuel used was 327 Gals. for an average of 9.8 MPG towing a 12000 Lb. fifth wheel. I don't think that to bad since my other truck with a 454 in it got about 7.5 MPG. Average speed on the freeways was between 65 and 75. As far as the hills, WHAT HILLS...Pulled them all like a champ. The old truck would bog down to 40 or 45, the LLY did them at 60+ . Very Pleased with the whole package. Started the trip with about 1800 miles and ended with a little over 5000.

Well, I've traveled city, highway, towing and empty with my 2002 and my new 2004 lly. My 2002 with 52000 on it when I traded it got 20.8 empty bebopin' around, but only 8 towing my 9000 lb. fifth wheel. That's pretty terrible considering I had a 425 Cat in a semi and got 7. I thought I might have got a bad one so I got a new lly. 6000 miles and I'm getting 16 to 18 empty and about 8 towing so far. I got about 17 on the '02 'till about 40,000, then it jumped to 20. We'll see how this one does. I hope it does better.


Mike

Seems odd that you would get 8mpg w/9000lbs. I drive like a freakin' lunatic, and am getting nearly 50% more mpg at 8000lbs (~16,000 combined) in very mountainous terrain. Something ain't right. The DIC said 8mpg going 75mph up a 6% grade.

Doesn't seem odd to me. On the 4000 mile trip my best was 10.11 on Indiana flatland, once. My worst was 6.7 in a headwind in flatland Texas. It was a short bed, hell, I had to stop four times for fuel crossing Mo. on I-44. I'm trying one more Dmax. If the new one isn't any better I'll have to try a Dodge I guess. Or an International DT466. Had one of those in '93 250 HP, left the house on Sunday night and got back on Fri. night and got 9, and never shut it off 'till I was at home.


Mike

Most LLY's aren't able to break 14.5 unloaded that I have been around. The only six speed truck I have seen does get much better though.


My best is 18.6 unladen and the worst was 14.9 towing 4,000 lbs. These were done by hand, my DIC doesn't have the mileage feature.


ROB

Hi Guys


I made up a spreadsheet program for Excell for my Duramax. I only have 2600 miles on it. I am getting 15.6 mpg since new and for my first tow I got 12.47 mpg at a GCWR of approx. 19000#. Hope the solo mileage improves as miles increase.http://www.dieselplace.com/forum/smileys/Big Smile.gif

I just pulled a 28 ft travel trailer, right about 7000 lbs for 1000 miles (850 interstate), and averaged about 9.5 by hand calculation, 10.2 by dic, pulled really well http://dieselplace.com/forum/smileys/Clap.gifat high speeds 75 -85 but the fuel mileage suffered. driving around 55 dic was reading 12.7. I have a total of 2300 miles now, stock

Well I went to Muncie over the weekend and took the golf cart and trailer(1500# max), running 75mph+.


My average is over 15mpg, I only had 100 miles on truck when I started now I'm over 500 miles so the heavy towing starts tonite.

You ran your new truck 75+ MPH for long periods of time with only 100 miles on it? Ouch.http://www.dieselplace.com/forum/smileys/Cry.gif


I always figured going easy on a new vehicle for the first several hundred miles would he benefical in the long run, and I especially wanted to do that with somthing whose sticker nipped at 50k. http://www.dieselplace.com/forum/smileys/Approve.gif But then I'm the sort of guy who babies all my "stuff". Every time I'm sold a car or truck the new owner wanted me to call him when I sold the next one!http://www.dieselplace.com/forum/smileys/Big Smile.gif

I have 2500 miles on mine and unloaded going throught the AZ mountains from Phoenix to Showlow i got 16.4 MPG round trip. Towing my 2500 lb pop-up camp trailer i got 15.5 MPG. This weekend towing my CJ-7 on a car hauler with T/H on and OD Locked out coming down the hill i got 13.8 round trip. While not honda civic numbers i am pretty pleased, my 5.3 Gasser was worse empty or towing, and i had to run at 4500 RPM to crest a hill at 60 MPH. All of these numbers are calculated using miles obtained by my GPS, since i have larger tires it is off by a small percentage. Incidentally the DIC is right on for fuel used, but the MPG calculations are lower than actual due to the larger tires.

A 2002 dodge dually (bro-in-law) and I towed similar high profile 10K+ trailers from CA to MO via I70 and back to CA on I80. We were together the entire trip doing 70-75 mph on the interstate and seemed to have a lot of headwind. 4,500 miles total, I averaged 10.6 and he got 11.1 hand calc'ed. Both trucks have boxes and we used them hard.

wow i must have a special truck or something. i get about 17-18 around town and 23-24 on the highway with the tail gate down. i go just over 300 miles on just over a 1/4 tank of gas on the highway!

My lly is 2.5 months old. I have 12000 miles of towing 8-10k pounds. I deliver all through the hill country around Austin Texas. First 2000 miles I averaged 12 mpg. Next 8000 averaged 13.. Now have beta lly with attitude and and now best has been 13.5. I put my lead foot using level 2 for a tank and still got over 12. Stock tires, stock exhaust for now.

When not towing, I get high teens on the interstates at around 65 MPH and low to mid teens around town. When towing my 36' approx 13,500# Toy Hauler, I get 11 at 65 MPH. So far only 3,000 miles on it. Hope it improves at least a little.

wow i must have a special truck or something. i get about 17-18 around town and 23-24 on the highway with the tail gate down. i go just over 300 miles on just over a 1/4 tank of gas on the highway!

yep you really have a special truck. Let's see, quarter tank on a SB is about 7 gallons or 42 mpg, or if it is LB it is about 9 gallons or about 33 mpg. That, frankly, can be found in a pile out behind the barn.

Jim

ya but it drops quick from a little less than a quarter. it drops maybe 2 times faster after a 1/4 tank. i get about 23 mpg with the tailgate down on the highway. i filled it at maine went over 300 miles then filled it down hear and i figuared it out to be 23ish. i dont remember the amount of fuel i put in or how many miles.


i figuared that some one was gona call my bluff. i take it easy most of the time. my rpms just go up to the shift point and thats it.

Well, I used the 1.039 formula to compensate for the 265's and I am happy to report that my mileage is up to 15.4http://www.dieselplace.com/forum/smileys/Clap.gif Now, that is not towing, but running some A/C. We are towing the trailer this weekend and maybe I will gain the extra 1 mpg. Hey, anything at this point helpshttp://www.dieselplace.com/forum/smileys/Big Smile.gif

Sonny, what is the 1.039 method?? I have 265's also maybe i need to calculate my different too.? My speedo is off at least 2mph at 70mph.

Might be a little late to chime in but...


Could the EGR and/or the CAT cause the LLY to drop mpg? Will chipping the engine help when chips are available? Maybe near 10,000 miles she will finally break-in and improve...


There is a lot of information out there concerning EGR'd diesels will likely suffer from a slight loss in economy when comparing apples to apples. I'm sure the CAT has some impact on economy as well--logically it would.


Here is a relevant and interesting article for your viewing pleasure: http://driversmag.com/ar/fleet_exhausted_uncertainty/


My wife's LLY/Allison 4x4 crew-cab has about 5100 miles on it. It has been getting 15.4mpg in town...average speed has been about 29mph. We took it on a trip to Florida after the initial break in at about 1400 miles. No towing just luggage for 4 on a 10-day excursion. The best tank that I recall was 16.8mpg with a speed average of 72mph--I remember this distinctly as it was the last tank full before we got home. The DIC appears to be accurate within a couple of tenths on the trip mpg. I take my sweet time filling the truck up allowing the foam to settle over and over until the settled fuel is in the top of the fuel neck. I fill it plumb full the same way every time.


16.8 is just okay in my book. We'll after another 15,000 miles or so what it does and then switch over to synthetics.


I am curious as to how things are going to settle out emissions control-wise on these trucks. Dodge/Cummins is going without the EGR for now. I personally like the idea.


I'm glad folks have realized that you must factor in the increased tire size when doing the calculations. I also note that some folks are still driving around with their tailgates down. I thought the myth that it gives you better fuel mileage had been put to rest through science.


Peace out

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Our 03 duramax with 9000 miles is getting 16 MPG (Canadian Gallons).About 12mpg American towing a 10000lb 5th wheel.


Leaving on a trip to North West Territories,Yukon,and Alaska in about a week towing same. Will post mileage after about 7000 mile trip.(If I don't run out of money before I get back)</TD></TR>
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Sonny, what is the 1.039 method?? I have 265's also maybe i need to calculate my different too.? My speedo is off at least 2mph at 70mph.


I noticed that you are running 265's. Are you correcting for the difference in tire size. If not you are calculating at a 3.9% error. Take your miles driven and multiply by 1.039, then divide by gals used. That sould give you correct mileage.


Ex.
Say you show 330 miles on odo...Multiply by 1.039 to get 342.87 then divide by gals. (from previous post by another member).

I am new to the diesel engines but extremely impressed with my LLY. I have a 24' Baja H2X boat that weighs in at 4000# DRY. Factoring in the 80 gal. tank that is aways about 1/2 full and all of the other crap on the boat is about 500#. the approx weight of the trailer is 1500+#. Not to mention all of the stuff my wife has me load in the truck. All in all off the hitch I have about 6000#. I avaraged 13.3 mpg from San Diego to Lake Havasu with average speeds of 65-70mph. Coming from a Ford V10 with a 29 galllon tank I always needs to fill up at least once in transit. Now I can make it on one tank of fuel that has 3 less gallons. I have been reading that everyone is bitching about their gas milage. Keep in mind that deisels dont start breaking in until 5,000-10,000 miles. I have 2500 miles on mine right now.


I also been reading about the LLY smoking like a brush fire. Mine did smoke alot at first but now has started to subside.

All milages have been from the DIC, it seems to be fairly accurate from what I calculated. Total milage out to Lake Havasu is about 280 miles. I had est milage left of 56 mile. If you calc out 13.2 x 26 you get 338. It was only a couple of miles off. I still need would like to do manual calcs to double check.

Itchy,


Did you get the Chevy or Gmc?

Around town I get 15 mpg, on long trips I get 21 mpg, towing 12,000lb 12 ft high 5th wheel to Florida and back got 12mpg.


Trip to Florida was with brand new truck with 1000 miles on it and 0 miles on repaired Allison. Allison had a seal leak and had to have some parts replaced.

Love these towing MPG's postings. Remember the days when 6-8 mpg was great for towing a fifth wheel? With the advent of PCM's and efficient fuel injection systems we are quickly getting spoiled to the higher MPG's. There are many variables that affect MPG's when towing, i.e. GCWR, tire size/pressure, frontal mass, wind, humidity, terrain, leadfoot, etc. A 14k 5ver should tow easier in Florida than in the hills of Kentucky. I know there is some physics puke out there drooling to chime in on this post. There is a point where the amount of air mass you are pushing up/around the truck and trailer begins to suck/hold you back. I don't recall the exact terminology for this. I have noticed it is much easier to maintain 60 than 70 and the MPG's are much better at 60. I tow heavy (17-18k) Sunnybrook 5th wheel with there new aerodynamic front cap (lol). I average 10-12, 8-9 in the hills. Not bad considering I'm pulling a small house. http://dieselplace.com/forum/smileys/HiHi.gif

I average about 7-9 mpg with lly.3500 miles on now but I believe right foot has something to do with that. No mpg complaints here, to get that much power we got to burn something

On a 4300mi round trip with our D/A 3500 SRW (7120lb empty) with a 11.5' camper and 5500lb car trailer, and our family/spares = 17,000lb combined weight on a CAT scale, we got just under 11 1/2 MPG calculated (12.6 DIC). Speeds were seldom under 65mph, and usually 75mph.


Our gasser used to get 7 mpg. You can say I'm pretty happy with 50% increase in fuel economy.

On a 4300mi round trip with our D/A 3500 SRW (7120lb empty) with a 11.5' camper and 5500lb car trailer, and our family/spares = 17,000lb combined weight on a CAT scale, we got just under 11 1/2 MPG calculated (12.6 DIC). Speeds were seldom under 65mph, and usually 75mph.


Our gasser used to get 7 mpg. You can say I'm pretty happy with 50% increase in fuel economy.





That is pretty good. I just completed a 4,400 mile round trip from MN through Coloado and averaged 11mpg. However, I only had my 4000 pound p/u camper on board (11,000 combined). The real killer was cruising 75-80 across SD &amp; NE in the wind, which would get as low as 8.5mpg average. I was getting 14mpg in the mountains, of cousre at much lower speeds!

Just completed an 808 mile trip through the Sierras in CA (I395). Used a total of 60 gals. I was very happy with that.





Bill

total weight 16,000 lbs.http://www.dieselplace.com/forum/uploads/Picture_038.jpg average 11.5 mpg on mostly level, some small hills (I am from the northwest,where a small hill is still pretty big)

I normally tow a boat and it weighs, with trailer gas and gear around 5000. (weighed at city dump/scales) I have found that i get about 2 mpg better w/out tow haul engaged. Shifts are smooth and fine, and with that load braking is no problem without trailer brakes. Undid my egr and my mileage just improved another 1.5 or more mpg! read that thread. I am not towing anything but a trailer loaded down with sandbags for friends and family tomorrow. This is in anticipation of CHarley!! I will post later on that mileage since the trailer with sand should be around 8k. Hope all is well for everyone else near the storm. It looks like it should be a good one. Storm surge is looking to be around 16 feet for Tampa, ouch, that means the tide comes in 16 feet over the normal 1.5 feet and a lot of people will see a lot of water. Near the coast they will have those 16 feet plus waves on top!! I will need a snorkel for my intake.... Will the engine short out??? Hope not. Dont worry, I dont plan on taking her swimming. Wish us sunshine boys some luck.


http://www.ssd.noaa.gov/PS/TROP/DAhttp://www.dieselplace.com/forum/uploads/1AB_20.jpgTA/RT/float-ir4-loop.html (http://www.ssd.noaa.gov/PS/TROP/DATA/RT/float-ir4-loop.html)Edited by: blowinsmoke

I was getting 5 with my gaser @65 mph now I'm getting about 9-10 mpg @ 75 mph with cruise on so I 'm happy. getting around 12 in the city.

Just got under a thousand miles on truck and got 11.5 MPG pulling a 6200 lb trailer for first time. Manually caculated fuel economy.

I had a 01 Chevy CC dooly with the Duramax and allison. Truck averaged 18 mpg on the hwy at 75mph, 16 mpg on my commute and 11.5 pulling 12k. The truck was chipped with an Edge Hot Juice. I did not baby it, drove it like I stole it. I put 122,000 miles on it. MPG over the time I owned it was pretty consistant. :)

My 05 GMC CC dooly with the duramax and allison has got a best of 14.5 mpg. Sad thing is that is driving it easy, not like I stole it. It gets about 13.5 on my commute. -:t I am less than happy about that.

Compairing the differances in MPG I fear I will get about 8 or 9 pulling my RV.

MPG on this diesel is not much better than a Big block. Diesel is 2.21 aound here and gas is 1.91. Which means it would cost less to drive my last big block 4.56 geared dooly than this diesel.

Most LLY's aren't able to break 14.5 unloaded that I have been around. The only six speed truck I have seen does get much better though.


I tend to agree. My mileage empty with a zf/6 ext/sb is consistantly over 20 driving a 20 mole daily commute. The truck has 1600 miles on it now.
Got 16 towing 4000 lb camper in the Pa. mountains last week.
I'll shift the gears myself without complaints, from what I'm reading it looks like the Allison needs to be fed?

Got to love a good mines bigger than yours thread heh?

Obviously there is something wrong with my truck. Just under 2500 miles and stock except for 265 Michelins. It is 4x4 CC. My definition of city driving is no freeways or highways at anytime. Stop light to stop light, never exceeding 50 miles an hour. My average is consistently in the low to mid 13's . If I throw in a cross town freeway run or two it jumps up to mid 14's................whoo hoo! I am old and slow, rarely to I spinner her up, conservative would be an understatement.

Last weekend pulled a load of dirt bikes and gear up to Colorado. I am guessing total weight of bikes , trailer and gear was about 2000 pounds. I ran between 60 and 70 the entire trip, did NOT push hard . I could not get above 14.8 mpg coming or going.:shake:


This has been the most disappointing part of my diesel experiance to say the least.

Just finished a 5000 mile trip from Phoenix to Tenn towing 7,000 out (~14500 lbs GCW) and bed load back (8200 lbs). I started out with 1000 miles on the truck and got 10 mpg out and 16.5 to 17 back. Speeds towing were up to 70 and non towing was 75 to 85. I would like to see a little better. I hope when it gets broke in it will improve.:grd:

Pulling a 12K 5er I average 12MPG. City driving is 17-18, and on the freeway I average 22 mpg on my O4 2500 2WD D/A.

I avg. 18.1 (12000 + mi)up hill, down hill, flat, city or hwy with the air or without. Avg mph is 46.3 I never carry anything. I had a 5.7 Hemi before before this Max the best it ever did was 13.5 so I am digging this 18.1 with diesel at $1.55 and gas at $1.94http://www.dieselplace.com/forum/smileys/Big%20Smile.gif Edited by: ntnbolt1

Southern California, Diesel $2.35-$2.50, Gas $2.30-$2.60, Damn Cali sucks for gas!

Southern California, Diesel $2.35-$2.50, Gas $2.30-$2.60, Damn Cali sucks for gas!

hey, did you check the date when that was posted, I believe that was just over a year ago.

Most LLY's aren't able to break 14.5 unloaded that I have been around. The only six speed truck I have seen does get much better though.


No way! I get 14-15 towing the weights the guy that started this thread is quoting. No problem beating 14.5mpg unloaded even with mostly city driving, and on the open highway its a sure thing at 70-75 cruise. I would expect at least 18 on the open highway unloaded, and maybe get more.

I hand calculate my mileage, the DIC reads about 1mpg higher generally, but of course is rendered completely useless by the tuner now anyway.

Pulling a 12K 5er I average 12MPG. City driving is 17-18, and on the freeway I average 22 mpg on my O4 2500 2WD D/A.


This HAS to be DIC numbers. Those figures are just too high and cannot be correct.:eek:

Is it possible that the NE/Kali emissions trucks get lower economy than Federal due to different emissions strategy?

Just towed our first trip to Yellowstone with our new 5er (Lakota, 35 ft., 14,400) .... plus two adults ... overall the mpg was 12.2 .. that includes mt driving and freeway ... and in T/M .... avg on freeway about 65 on mt road 50 ... short trip for us about 5 hours .. was pleased with mileage .. had a smaller 5er last year (28ft., 9000#) avged a little less ... taking a 3 month trek back East this fall .. hope mileage holds ..

This HAS to be DIC numbers. Those figures are just too high and cannot be correct.:eek:

This is not the first time I've seen negative comments about the accuracy of the DIC's (what a poor marketing choice?!?) MPG figures.

I've only done 500 miles on my LLY with no pulling yet, but I have 17K on my Yukon XL V8100 with a lot of it pulling 10,000# and I find it's DIC and my co-pilot's (SWMBO) manual calculation to be very close; and on the long hauls, its right on the money.

While I did notice that the DIC on the Yukon SLT is slightly more sophisicated than the Sierra SLT's DIC ( the Yukon gives instanteneous MPG consumption as well as average MPG and a few other nice things that I was disappointed to see missing on the Sierra) but they can't be so different that the LLY's DIC can't be trusted, or can they?

I start pulling with the LLY on the 4th of July and I'll report both my wife's manual and my DIC's results when I return (it is only 500mi round trip but that is at least one full tank of gas which should be enough for comparison).

I should note here that both vehicles are 100% stock from the factory.

hey guys i'm glad to hear some of you are getting decent mileage. I have a 10000 lb toy hauler 5th wheel and a pulled it from salt lake city to lake mead and back and averaged 7mpg cal by hand and 6.5 on the computer. I was pretty upset considering I just sold my 2000 powerstroke and never got below 13mpg. My duramax only had 3000 miles on it but come on my mileage isn't going to double after its broken in. My brother-inlaw got 11mpg pulling a 5th wheel that might be 1000 lbs lighter with his 2002 powerstoke. How are your egts on these new trucks? If I pull any hills at all I hit 1350 on my edge attitude monitor, even if it is on the stock setting.
Someone please tell me there is hope.

hey guys i'm glad to hear some of you are getting decent mileage. I have a 10000 lb toy hauler 5th wheel and a pulled it from salt lake city to lake mead and back and averaged 7mpg cal by hand and 6.5 on the computer. I was pretty upset considering I just sold my 2000 powerstroke and never got below 13mpg. My duramax only had 3000 miles on it but come on my mileage isn't going to double after its broken in. My brother-inlaw got 11mpg pulling a 5th wheel that might be 1000 lbs lighter with his 2002 powerstoke. How are your egts on these new trucks? If I pull any hills at all I hit 1350 on my edge attitude monitor, even if it is on the stock setting.
Someone please tell me there is hope.

7 mpg is not right. Are we missing some pieces to the puzzle? What size are your tires? If the tires are non stock, have you reprogrammed the odometer? How fast were you driving? Is the truck a dually? Is it lifted? Was there a head wind? All these items will impact the fuel mileage. If your truck is stock and you did a valid fill, then the truck has a problem. I would expect about 11 or 12 miles per gallon driving 65 mph, with a SWR truck. You should consider adding a "signature" containing details on your truck. It is a great help to others when trying to answer a question tailored to your situation.

Also keep in mind that all diesel pickup trucks produced after 12/31/03 (that includes the Dodge and Fords) took a fuel mileage hit due to the new emmission requirements. The LB7 gets about 3 mpg better than a LLY. The Ford and Dodge sites report similar changes on their products.

On edit: What year is your truck? GM came out with a reflash around 9/11/04 that applies to all 2004.5 (LLY) trucks and the first couple of months of the 2005 trucks. It may help your mileage about 1/2 mile per gallon or more. Also, check to make sure your air filter is clean.

ntnbolt 1 are you serious about the $1.55 diesel? Up here in South Dakota diesel is more expensive than gas and it is at $2.35 right now. If it's true man that is cheap.

never mind I'm just stupid I didn't realize that you posted that last year. I didn't even look to see how many pages this topic was.

i have heard the lly power pup is giving another 3 mpg with the additional power to bout, might want to give one of them a try

mine has 2800 miles on it the day afrer i got it we drove from dayton ohio to gatlinburg tenn. i got 19 mph average onthe interstate .got home imediatly hooked up my 21 foot toy hauler loaded with 3 quads full bed of fire wood plus some concrete from an old side walk to put in some holes in the road at the farm ant drove to campton ky and i was not babying it either 75 to 85 mph all the way and got 14.5 i must say i love the truck my old truck was an o3 hd 6 liter big diffrence

I agree with BH, 7mpg is way outta line. I would expect 13-14 at worst towing 6500lbs at 70-75. Maybe drop that to 12 over lotsa hills and some wind. This is what I would expect WORST CASE.

I have nailed 16+ no problem pulling that light a load.

Thats just not enough weight to bother the Dmax down to 7mpg.

.

I tow a Davis Boats Bahia 25 on a tri-axle weighing in at about 10,000 pounds and get 10 to 11 mpg with my 2002 Dmax. I drive a fairly hilly section of freeway. Depends on how you drive it too. Yea I know, I am new but thought I would chime in.

I tow a 33' WW toyhauler that is 12k. I have got 9mpg towing from Tucson to Phoenix and 8mpg towing from Phoenix to Sedona round trip.

I have a Jan05 crew cab short box Allison,285 tires, recalibrated speedo, currently has 7K miles on it.
I drive 25 miles each way to work through mostly rural 55mph 2 lane and average around 15mpg (measured from tank to tank, no DIC)
I pulled my 6300# 27ft travel trailer to Florida from Michigan in March with only 1500 miles on the truck and was lucky to get 10mpg, some tanks were as low as 8.5 mpg when the wind was bad.
I pulled the same trailer around 500 miles round trip this week and was still at the 10mpg or less range. return trip was in 93 degree temp and the engine fan kicked in every time I pulled any kind of a hill, I could tell that wasnt helping my MPG. Anyone who has ever been to MI knows it aint all that hilly here. I usually run 60-65 MPH with the trailer.
I really hope something shakes loose soon, I am having a hard time justifying the extra $$$$ for the d-max when I was getting the same mileage with my previous gas truck.

BH my truck is stock with the exception of 265 tires and 1.5 in of leveling with the torsions. I've pulled my trailor now a couple of times and the mpg are the same. There hasn't been any wind and not any significantl hills to pull. I'm getting 14.5 mpg on flat freeway going 75 with ac on. I also have the edge juice, I pull with it on level 1 or zero and the result is the same. My egts hit 1350 the second I hit a hill.
It seems to me that it defeats the point for emissions components if you burn twice the fuel, it has to end up being close to the same.

You are actually travelling a little farther than your odometer is showing because of the 265's.

Maybe your mpg's are are higher than you think.

.

My latest DP MPG calculated towing results from J'ville to Myrtle Beach SC and back. Going up: 70mph @ 8.5mpg; coming back 65mph @ 10mpg. Backing er' down a bit seems to help. I was at 25,500lbs GCW on this run. JJ :)

SonnyBear,


I noticed that you are running 265's. Are you correcting for the difference in tire size. If not you are calculating at a 3.9% error. Take your miles driven and multiply by 1.039, then divide by gals used. That sould give you correct mileage.


Ex.
Say you show 330 miles on odo...Multiply by 1.039 to get 342.87 then divide by gals.


Hopefully that is your problem. For what its worth, I have an early 04 LB7 and the best I have gotten so far is about 18MPG. The lowest I have gotten is 11. That was towing 6k through the mountains. I average about 12 to 13 in mixed. I have 5k on truck so far. I am also running BFG 285's. I am sure if I went back to stock and drove under 60 I could get 18-20mpg, but what fun is that?


BillEdited by: Redapple
I'm curious what the calculation is for 285/75/ r 16's is?

Welcome to the party!! Been there done that. I will save you tons of trouble. DO NOT CONTACT GM. Fuel mileage is not rated on these trucks so they will stick their head in the sand and say " We feel there is no problem and there fore there is nothing we can do at this time". :grd: