LLY Mileage

[rickdlance]

What kind of mileage are the LLY engines getting. Mine is not that good and dealer says there is nothing wrong.

[Mile Hi Guy]

I hate to say it but my mileage is well below what I was hoping for.

All highway at 75 posted is low 16's
60% highway/40% City is mid 14's

If I tow my boat (4,500 lbs) 15% of the tank I am mid 12's

My 97 Tahoe that I put 140,000 miles on would do the similar work at 1.5 to 2 mpg better. :confused:

I have 265 Mich. Tires and have corrected the milage and speed by 5% as I have closely calculated the difference.

First Diesel and disappointed in power and economy so far.

[ 06-15-2004, 10:35 AM: Message edited by: Mile Hi Guy ]

[dakotakid]

Just out of the box, my 04 seems to be quite a bit better than my 02 was. I pulled my camper with the 02 when it had 500 miles on it and it averaged 7.3 or something for a 3000 mile trip. I pulled the same camper with my 04 on a very short trip last week with 500 miles on it - and it averaged somewhere in that 10 range. I don't have enough miles on it yet to make a final judgement, but so far I think it is a big improvement over the 02...

Pat

[mark45678]

At speeds slower then 75~80 you will see some improvement but at speeds over that the lb7/lly are the same! the lly has more low speed grunt for sure! my lly is getting 17 mpg at 80 mph,19+ at 65 but I cant drive that slow :eek: .... towing a bread box that tips the scale at 7500 lbs 12 mpg at 70~75 mph

[4diesels]

Unfortunately the only guys getting good numbers are the ones that keep it under 70mph. Beyond that, both my '01 and '03 trucks get terrible milage for a diesel. My '03 with 28k on it has an average on the trip computer of 13.2. I wouldn't even own the truck anymore if it wasn't for the very comfortable interior. If Dodge ever puts a decent seat in their truck look out. Alright, seats, stereo, dash, trans temp gauge, etc., etc. BUT, my '03 Cummins HO automatic with 3.73 gears knocks down over 19mpg cruising at 80-85, and is better yet slower.

[LanduytG]

OK just filled up the )4 for the second time. First tank was from the dealer so not sure how much was in it. Anyway all city driving I got 17.4 and I don't think thats bad at all for a new out of the box truck.

Won't get any really good hiway numbers till I go the the pull off in July.

Greg

[carco]

First 5500 miles, DIC reading 16.2 total ave. Worst tank , wife driveing pushing 90-95 in Fl. 13.7 mpg. Fl. trip ave 17.3 mpg. WV. ATV trip 460 miles w/ 4500# trailer and 5 in cab 16.2 mpg, hills and 65-70 when possible. bob....

[rickdlance]

Finally got to run the 01 and the 04 together. 04 got 2 to 4 mpg worse. Pulled better in high gear only. Once the 01 downshifted it ran off and left the 04. Both trucks were loaded the same and we went from Missouri to Tucson at 16,000 pounds GVW. At 1 point the 04 went silly and would not hold speed on level ground, temp went up and fuel went down. Shut it off for 1/2 hour and it was back to normal.

[jakey]

Just filled up, DIC says 17.9mpg. Half and Half, highway and back road driving mix. With speeds from 45-75. Got 600 miles on it so far.

Guess I need to update my signature. :D

[More Power]

Rick,

EGT plays a big part in engine temperature - high EGT's usually accompany higher engine temps. This plus the fact that the '04 is down on power would tend to lead me to a VNT turbo issue.

Gauges could help determine whether boost pressure was more or less correct.

MP

[Benoni]

I got 20.8 mpg on my first shake out trip with a lly. Granted, I was trying to stay under 55 for the breakin but the trip was from Colorado Springs to Leadville (10,200') over 3 passes so I was pleased!

[FlyRod]

My New LLY is treating me good so far(1800 miles). The fan noise is disruptive if you are pulling a load in the hot Florida sun. If it makes it run better, I can live with it. It usally does not last long.

I am getting about 17.5 MPG at 78 MPH with the air conditioner going. I noticed as others have that slowing down even to 65 MPH can make a big difference.

[Darip]

I took my LLY to the dealer today to see about the mileage,the clutch fan running even when not towing anything, and the loss of power. They called and said that GM has a bulletin out on running larger tires and the loss of power and also a bulletin out on running oil bases air filters. They said that my Mass Air Flow sensor is covered in oil and needs cleaned or replaced. They want my stock filter so that they can run a diagnostics without the oil based filter. I will hopefully know more tomorrow. If any of you have learned anything new, it would be greatly appreciated.

[FlyRod]

I have a theory that if you leave your $40,000 machine alone and not fall prey to chip pushers and K&N pushers, you will have a better experience.

Let the $100,000/ year engineers at GM worry about the complicated stuff. These new diesels are so highly engineered, balanced and computerized that any shade tree monkey business is sure to cause problems. I

[mcmonroe]

I am new - so be gentle with me. I do think that FlyRod might have some good points.

After reviewing most ever thread on this forum and seeing the various issues that many are having -- it does seem like more than a coincidence that many of those with "problems" have done modifications to their truck etc.

It only makes sense that if you change the grill to something more restrictive that you might run into cooling issues with regards to the radiator, A/C or the power via the charge cooler.

It only makes sense that if you change the air filter to one that contaminates various sensors with oil etc that the truck might not run right as a result, etc.

Just this morning I saw a truck pass me coming into work that had a sheet metal grill that had flames cut out on it. I would bet that at least 50% of the surface area was covered by sheet metal. How freaking smart is that. (huge grin>

:)

Mark

[Albee]

Cant speak on a LLY, but my 02 CC, LB just got 20 MpG on a highway trip. That is the best I have seen on it yet. 19 was my previous best. Average around town is 15 to 16. In the winter will get closer to 14. Trip was from Smithville Lake in Mo. to Cheyenne, Wyoming.

[jaoder]

My LLY 04 CC 3500 Dually automatic with about 7500 miles is geting between 17-22 not loaded on level ground at 60-65. I pull a 40' enclosed gooseneck car trailer with 6" of extra height. Pulling at 60-65 MPH it getting an average of around 10.5-11MPG which I think is pretty decent considering the load. The trailer weighs in at 11K and both the truck and trailer weigh in at 22.5K when loaded. This is my first diesel and I waited for the LLY and so far I am very happy with it.

[rickdlance]

jaoder , Wanna trade?? Please??? I am in Nevada on interstate 80. I weigh about 20,000 pounds and my last tank was 6.9 mpg and the truck could not hold the speed limit with any grade at all. A decent hill would drop it to 3rd gear and 45 mph.
HELP! As of Monday truck should be qualified for lemon law.

[Benoni]

I replied previously regarding mileage during the 500 mile breakin. Now that its somewhat broken in & going a lot faster, recently got 19.5 mpg going from Colorado Springs to Leadville, with some side trips & back.(up & down 3 mountain passes of around 9600' each way) Also, went to the top of Pikes Peak today (6800' to 14,100 & back down. Averaged 14.5 mpg (7 mpg going up) & performed flawlessly. The Allison worked great breaking it coming down.

Silverado 2004 2500 HD Crew. LLY

[DURA-MAX3]

My new LLY is not up to snuff on mileage either. I am only getting about 6 to 9 MPG at 65-70 miles/hour pulling my trailer that weighs 7000lbs. My 01 D/A was getting 12-14 at 65-70 miles/hour pulling the same trailer. The power does not seem that much better either. This new truck seems to have a lot of turbo lag from a dead stand still. Not sure i would trade again if I had known the mileage was this poor...Have not had it in for a check up yet but may have to soon. It is only averaging about 13 by itself... :mad: :mad: :mad:

[rickdlance]

DURA-MAX3
Does your truck ever go over 210 degrees? My dealer has tried everything. I have 3 injectors that are out +- 6%. On my old truck I had one drop to 3.5% and my mileage dropped about 20%. Dealer sent info to GM and they said this was not the problem. I am trying to get the Lemon Law to take over.

[Mile Hi Guy]

Well I am new to the boards to and I hate to keep posting negative impressions but I too am disappointed.

Rick, my temp is constantly right at the 210 mark and the fan comes on frequently even when unloaded.

Dura-Max3, I too have a lot of lag at a dead stop. It is almost like its worse if you floor it. Much worse than the other diesels that I have driven. My mileage also is lucky to break 14 - empty.

FlyRod, engineering? my lly does not pull like by buddies 02 trucks and uses more fuel doing it? I will take this thing down to the local strip (Not the intended use but will give an equal ground comparison) and see what it runs. If it breaks 19 seconds I would be surprised.

At 5,000 miles, maybe it needs more time. I hope so, with the work plan I am stuck with it for 5 years min.

[DURA-MAX3]

Yes the engine temp is always around 210 and the fan comes on constantly. That is annoying me. It seems to be tied in with the braking somehow. I can be going down the road and start appling the brakes with the tow/haul mode on and the engine fan will kick in right before the truck comes to a stop, then will stay on robbing the motor of power on take off...My average mileage in the DIC is 11.9 for 4 tanks of fuel only 1 tank pulling my trailer. I have been told that since I have changed my tires to 265's that the DIC would be off a little, so the best i can tell the average is about 12-13mpg. At 70mph I am actually going 72mph...Somethings gotta give soon, this thing is costing a fortune to own compared to my 01D/A...

[hitman]

I also have the lag when I floor it from a dead stop. Feels like my old 6.5 would beat off the line.

[TDiesel]

I have just over 3000 miles on my LLY I have to agree that the turbo lag when you floor it is more then my 6.5 I just traded in. I found if you only put it half way down it seems to respond better. The computer says I am getting around 16 mpg average. On long trips I get around 19 mpg at just under 75 and when in town with a heavy right foot I am getting around 15 mpg. The mpg is still better then my 6.5 Burb and my 1/2 gasser.

[LanduytG]

It will run around 210* because the t-stat is a 205* I think. As for the fan coming on when stopping its would be because you have less air flow to keep it down. As you slow down the engine will heat soak a little and the fan could come on. After a its on a bit it will shut down.

I love my LLY 17.5 around town, and I will find out next week what it gets on the hiway going to the pull off.

Still better than the old 6.5 any day of the week.

Greg

[jakey]

I have to agree with Greg, I love mine too. My old 6.5, the temps would run to 220 to 230 before the fan clutch would kick in. Sometimes would kick on at 210. Seems it had a mind of its own sometimes. With the new truck, it'll kick on before you even see the temp gauge go up, as mine has never moved off the 205 reading on the gauge. Maybe if your fan clutch is kicking on without reason, it's because the fan clutch is a little quicker to come on than others ? Just a guess, but switching the fan clutches between the 01 and the 04 would rule out that question ?

[dodgerfan]

This being my first diesel all the comments about mileage and reliability had me worried, but I thought I'd pass on some positive thoughts from my early experience.

Just completed a 4000+ mile road trip, started with just over 3000 on the odometer. Moderately loaded I suppose with 4 people and the back full of gear, but saw all types of driving. Enjoyed the "speed limits" of Montana and Wyoming, a couple days of slow-and-go in Yellowstone, pulled strong up 8% grades to over 12,000 feet in Colorado, saw 120 degrees in Death Valley, LA traffic jams...

About the only time the fan came on was when I was passing cars going 75 up some of the grades on I-80 in Nevada, with 100 degrees outside. Never saw the temp gauge move off 210. Average mileage for the trip was 17.9, a whole lot better than my old truck would have done. My impression is that this is one strong engine/tranny, all wrapped up in a real comfy package, plus it gets darn good mileage for something that big and heavy! Not a bad combination at all, glad I switched!