All this 17-20 mpg wether its highway or city is all foreign to me . I have an 11 with 10000 miles and have always averaged 13.5 mpg with combo of city and highway driving .
I took her n earlier this week for the flash for the po299 dtc that i only got once and recieved doc2558332 bulletin reflash . I have also noticed once maybe twice the steam from under the hood passenger side but at the time didnt know ....thought maybe it was steam from it being so cold .
I guess im just wondering how this is so diverse ....from 10mpg to 22mpg .
Priceless - There is a HVAC drain hose on the right side of the firewall on the engine side - down at the bottom. If the hose is not turned towards the 8-9 o'clock position it can leak onto the exhaust and lead to steam and a faint diesel smell. Often can be noticed at slow speeds when making left turns. I had this on a truck I was driving and made it go away easily by turning the hose. Hope that might help.
Anyone claiming 17-20 MPG in the city needs their head examined or needs a clear definition of city driving. The LML definitely gets better mileage than the LMM stock vs. stock, but it's still a heavy truck with a 400+ CID engine. I average 14.5 MPG pretty consistent with a mix of city and highway driving, and if there isn't a head wind (good luck in West Texas) I can manage 18-19 MPG, depending on how heavy my right foot is. FYI, I'm about to roll over 18,000 miles on my truck. I am very pleased with the mileage for a 100% stock truck that gained another 700 lb. of weight over the previous truck. It seems to average what my '08 LMM did with a tuner and exhaust. I think that's doing well considering the truck will regen once per tank of fuel!
Anyone claiming 17-20 MPG in the city needs their head examined or needs a clear definition of city driving. The LML definitely gets better mileage than the LMM stock vs. stock, but it's still a heavy truck with a 400+ CID engine. I average 14.5 MPG pretty consistent with a mix of city and highway driving, and if there isn't a head wind (good luck in West Texas) I can manage 18-19 MPG, depending on how heavy my right foot is. FYI, I'm about to roll over 18,000 miles on my truck. I am very pleased with the mileage for a 100% stock truck that gained another 700 lb. of weight over the previous truck. It seems to average what my '08 LMM did with a tuner and exhaust. I think that's doing well considering the truck will regen once per tank of fuel!
I have 8112 miles on my 2011 LML. I have purchased 665.1 gallons of fuel since I picked it up. That's an average of 12.2 mpg. This is all hand calculated. I have kept a log since purchase. These numbers are true and accurate for my truck. I would have to say it is a 50/50 mix of city and highway.
I have 8112 miles on my 2011 LML. I have purchased 665.1 gallons of fuel since I picked it up. That's an average of 12.2 mpg. This is all hand calculated. I have kept a log since purchase. These numbers are true and accurate for my truck. I would have to say it is a 50/50 mix of city and highway.
my info on my OnStar app shows 14mpg lifetime and 10854 miles and i live in southern California so even some of my highway mile are like city miles and i tow 36foot bumper pull toy hauler @13klbs every other weekend. I have had my truck seance November 5th 2010
I have come to the realization that these trucks like to run....fast. In town, I'm looking at 14-15mpg. At hwy speeds of 70-75, its about 16-17mpg. For some reason, the 80-85mph get me the best mpgs......like 20mpg+. I picked up this truck on Oct 1 and just rolled 14,000 miles this morning.
I have come to the realization that these trucks like to run....fast. In town, I'm looking at 14-15mpg. At hwy speeds of 70-75, its about 16-17mpg. For some reason, the 80-85mph get me the best mpgs......like 20mpg+. I picked up this truck on Oct 1 and just rolled 14,000 miles this morning.
My truck was averaging around 20 mpg running 78 down the interstate, but at 65 I'm getting 16-18 with it just rolling over 3000 mi before I put it in storage. I'm in Idaho so those numbers depend on the wind. Wither way it is better than my LMM with Ram Air and exhaust.
I agree that these trucks wanna run, i have to use cruise on base and in town.
I have not hit 80 MPH yet, but I have noticed that the traditional 55 MPH that usually gets the best mileage does not with my Denali LML. Maybe the MPG sweet spot on these new LML's is closer to 80 MPH, very interesting.
I can get up to about 17 on the freeway until the regen kicks in, then it's usually when I need to get off the freeway. After that driving in the city in regen mode my mileage will drop down to about 13. After the regen is done my mileage will creep back up to around 14.
I am guessing it is a combination of the gearing and optimum RPM of the diesel. Maybe the 2011 Allison has a taller 6th gear that lends itself to better MPG at 80 MPH. It would be interesting to see the GM results of air flow testing at various speeds. It is possible that the aerodynamics at higher speed increases volumetric efficacy, both airplanes and boats prove this in many cases. No PHD here, I just hang out with them.
Either way, I am with you, I also love the idea that 80 MPH gets the best MPG.
If you're getting 16-17 MPG with ALL IN-TOWN (i.e. Stoplight to stoplight, stop-and-go traffic, etc.) and counting regen you should never get rid of the truck! You cover my LML and my previous four Dmaxes by 2 MPG in the best-case scenario.
My truck pulls heavy loads better at 70+ MPH, but I can't say that I've seen a noticeable difference in mileage.
45 miles each way to work, mixture of city (0-35MPH) and country highway (55-65 MPH) roads....overall average of ~3700 miles, including the regen cycles, so far is 18.6 MPG. Best I've seen so far was a long stretch of highway with cruise set at 70...22.0 MPG....bone stock. Life is good!
I'm sorry but I have to wave a BS flag on these claims of people averaging over 20 mpg. Show me a 2 minute plus video with gauges and window shots on highway (not all downhill) averaging 20mpg plus, and then my truck will go in for service. Because that is simply NOT the case here in NY. My truck 2500 miles on my 3/4 lml is around 14 average and 18BEST CASE on the highway unloaded on level road at 65
I'm with you. Maybe good ol' NYS screws around with the fuel. Maybe it doesn't have the energy content of diesel available elsewhere (truckers would have the best info on that theory). I avg about 13-14 with the truck in my sig. EFI Live and all. I'm not a saint driving, but I also keep my foot out quite a bit. Cruise at 70 max and I do tow frequently but not crazy heavy. Bottom line is, no change of habit really seems to improve it much. For all the technological advancement in HPCR injection and turbocharging, 6 speeds etc, I would say they should be WAY better than they are. Even with a 60 mile per day straight highway commute, cruise locked at 65 I avg'd 17 MAX. If I was lucky.
I can see the how people are getting 20 mpg, but it's driving about on a flat highway at 60-65 mph, no load, and resetting the Average MPG right after the regen cycle. Like I've said, driving on the freeway at 75-85 mph I can get around 17, but as soon as the regen kicks in and driving in town, that'll drop the average mileage faster than cat stepping on an open electrical wire. But then again, I haven't really tried to do a mileage run and I'm not the most conservative driver either.
I'd hate to see what my mileage is in town during a regen cycle.
I get 17-18 on flat highway with a tailwind. LML CC/LB
But the truth is I didn't buy this monster for the good mileage!!! I bought it because I need it to haul and tow ANYTHING I give it. If I wanted mileage I would suggest a Prius or a Civic.
I have a 2010 Jeep Rubicon Unlimited - best MPG is 20 MPG on flat-Gutless
2005 Hondy Odyssey 18 mpg on flat HotRod
2002 Winnebago Journey CAT Diesel - Best 10 MPG on flat/tailwind
2005 Silverado - Same as LMM
1998 Jeep Wrangler 15 MPG DOG over 20 MPH.(rock Crawler)
2005 AC Cobra Factory 5 Replica small block - DON't Know/DON't Care!
I guess my point is that a truck that weighs almost 7000 lb. AND gets better or as good as anything else I have AND is a MONSTER is just plain Awesome!
I am still learning with this new truck but I averaging around 16-17 mpg with city/highway/short drives. One thing I just picked up on one must keep the rpm in 1500 range in what ever driving conditions, this causes me to speed within the city. Over 1700 the mpg numbers will fall.
As for me these numbers are great compare with my old LLY, the best I could do with it was 14-15 mpg doing same driving and same route but never be close to my first LBZ. I know numbers with improve with time this new truck.
What works for one person may not work for some one else, one must learn what works best for themselves. Secondly avoid idling as these trucks didn't like and burn up a bit of fuel.
Regen only uses .5-.57 gallons and it only makes about a .75 mpg difference at hwy driving. A bit more in city driving. I really don't care what you think I should get because I know what I do get. Only thing I'm disappointed in is towing milage is not as good as the LLY I had. LLY averaged 12mpg life time towing. So far the LML has been 10.3mpg. But it will pull 15K 70mph up and down hills with out even breaking a sweat.
my lifetime according to the OnStar app is 16 MPG at 12559 miles.... I have noticed that if you can manage to keep your foot off the Go pedal, you can get 15-17mpg in town. you just cant be putting more than 25% throttle... except for a few short bursts. on the highway though, i havent cruised anything less than 70, and avg around 18 mpg or so
The other side of the mileage coin was today when I got slowed down behind a semi... The pickup behind me was weaving back and forth across the center line wanting to pass me and the semi for nearly a mile... I could see him in the mirror and he was saying bad words... When the hole in the oncoming traffic came the ahole in the <brand deleted> pickup who had been tailgating me like I was the problem, whipped out to pass at the same instant I did... I could see him yelling...
The look on his face as I rocketed away like he was in neutral: priceless...
It's only been a couple weeks, but I'll tell ya I sure miss the mileage of my '03. I'm hoping she gets better with some miles on her, because right now she is sucking almost twice the fuel.
OK so for you guys that have been asking about millage today i did a little test for you and i got 17.7mpg that is without re-gen because it hasn't happen on this tank yet. the 17.7mpg is a mix of open highway, LA traffic on the highway and downtown LA city driving. so it was a good mix and that's what i got and i used just about a half tank.
Alot of folks dwell on RPM's equating fuel mileage. Lower RPM's should net better MPG and that is not always true. It is very possible that at 65mph the motor is slightly lugged and the ECM adjusts fuel rate. At 80mph perhaps that condition isnt present and the most efficient fuel rate per RPM is achieved.
My 7.4 gas motor runs much more efficiently at 2400 rpm than when it is in 4th/lockup and only hitting 2,000 rpm, my 03 Duramax gave similar results when keeping the RPMs ultra low.
Lugging is worse that winding for mpg, but the biggest factor is the parasitic drag. Our trucks just aren't aerodynamic. Mileage gets progressively worse as speed increases because it takes more HP to move the truck. That overwhelms small differences in rpm.
Now I'm seriously curious about the MPG-speed-gear relationship. I go to work at 55mph, because that's the speed limit, and the State Patrol and county Sheriff's cars are all over SR-14. Had one following me for 15 miles of a 23-mile commute today. So speeding up isn't an option on 14... but I am going to try driving I-84 (other side of the river) @ 65 mph, and see if my average mileage comes back up. Maybe I'll try a couple trips down 14 with the transmission in manual mode and set to 5th. At 55mph, that should be 1600-1700 RPM, instead of 1300-1400 like it is in 6th/lockup.
I'm realising that my two previous fill-ups were more mixed-speed, and those averaged 16.2-16.4mpg. Everything from stop-and-go in downtown Portland to interstate freeway. This tank, showing 14.3 on the DIC (which has proven to be optimistic), has been almost exclusively commuting at 55 mph for ~20 miles each way, with a couple miles of in-town on either end. I wonder if 55 really is worse than 65. Peak fuel economy is all about running the motor at max excess power... which isn't 1300-1400 RPM.
For those hung up on drag... I work in the aero industry. My degree is in aerospace engineering. Yes, drag rises with speed... but power rises and falls depending on where you're at in the rev range. If I increase my speed a little and my drag goes up by 5%, but my power available goes up by 10% or more due to the change in RPM, I'm using a smaller fraction of my available power, and that would result in better fuel economy. Getting better mileage at 65-70 than at 55 is entirely plausible. Example: the C6 Corvette is known to get better mileage at 70 than 55, because it's lugging the motor if you use top gear at 55. I'm not sure I buy the 80mph-peak-mpg when towing claims, but I haven't seen their data, so I'm not going to impugn those board members. If that's what their calculations show, good for them.
Now I'm seriously curious about the MPG-speed-gear relationship. I go to work at 55mph, because that's the speed limit, and the State Patrol and county Sheriff's cars are all over SR-14. Had one following me for 15 miles of a 23-mile commute today. So speeding up isn't an option on 14... but I am going to try driving I-84 (other side of the river) @ 65 mph, and see if my average mileage comes back up. Maybe I'll try a couple trips down 14 with the transmission in manual mode and set to 5th. At 55mph, that should be 1600-1700 RPM, instead of 1300-1400 like it is in 6th/lockup.
I'm realising that my two previous fill-ups were more mixed-speed, and those averaged 16.2-16.4mpg. Everything from stop-and-go in downtown Portland to interstate freeway. This tank, showing 14.3 on the DIC (which has proven to be optimistic), has been almost exclusively commuting at 55 mph for ~20 miles each way, with a couple miles of in-town on either end. I wonder if 55 really is worse than 65. Peak fuel economy is all about running the motor at max excess power... which isn't 1300-1400 RPM.
For those hung up on drag... I work in the aero industry. My degree is in aerospace engineering. Yes, drag rises with speed... but power rises and falls depending on where you're at in the rev range. If I increase my speed a little and my drag goes up by 5%, but my power available goes up by 10% or more due to the change in RPM, I'm using a smaller fraction of my available power, and that would result in better fuel economy. Getting better mileage at 65-70 than at 55 is entirely plausible. Example: the C6 Corvette is known to get better mileage at 70 than 55, because it's lugging the motor if you use top gear at 55. I'm not sure I buy the 80mph-peak-mpg when towing claims, but I haven't seen their data, so I'm not going to impugn those board members. If that's what their calculations show, good for them.
Your mileage willl be worse at 65-70 that it will at 55. It is very easy to see on the DIC and I have backed that up with hand calculations on many pickups.
You aero engineers can theorize all you want , but take it from a guy who was a USAF pilot for 24 years and experienced firsthand the effects of various types of drag--parasitic drag is a huge drain on power and efficiency. There is no L/D max on our pickups.
Well, 2 trips into CA over the past week - where the max speed when towing is 55, have resulted in better mileage, I do force it into 6th when she wants to stay in 5th and as much as I don't like CA I did admit to myself yesterday how at least I am saving $$ driving here (due to the fact I don't buy my fuel here of course). I can also say with assertion that my 8' wide trailer costs me about 1 MPG over my 7' wide trailer under the same conditions, same roads, etc, the weight has some what of an impact but no where near as much as RPM and wind drag.
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