LMM mpg? - Page 3

Billr · 09-02-2007, 09:38 AM

We have just turned 500 miles. The first tank (mostly local) was (hand calculated, acutal gallons put in the tank) 12.5. However I have noted the variation in filling caused by fuel "frothing" when filling the tank. So this number is suspect. I assumed the tank was fully "full" both times and this may not have been the case. The truck was driven with a light foot and svwith what little highway driving driving we did was well below 70 all of the time. I would love to get the numbers up in the 16's but suspect that the LMM's with all the controls are only going to do in the 13's initially. Towing for us is going to be the real tale. The new tank will give us a much more solid number. I have noted a large variation from the DIC millage from the hand calculated (actual gallons used/miles driven). The DIC millage was much higher. I verified the miles driven by GPS which has proven to be very accurate. The DIC was showing almost 16.

Fish · 09-02-2007, 09:47 PM

Has anyone had real mpg improvement from a aftermarket product ( Tuners, air filters, ect) ?

07DirtyMax · 09-03-2007, 12:04 AM

I have an Edge Juice w/ Attitude and an AFE Stage 2 on the truck already, 7000 miles on the truck. I saw like 10mpg when I first got it and it went to about 16mpg with city/highway combined driving. I installed the intake and chip at 5000 miles. I use the chip primarily on the tow setting and routinely take it to 100 mph and I'm seeing 22mpg on the highway and about 18 - 19 in the city. Could be it breaking in or it could be the mods.

Note: Also, with the Edge I can monitor a ton of stuff and I had noticed a few posts here about EGT's during hard pulls or regen. I can read the EGT's off the module from the sensor I installed in the manifold and I have very rarely ever hit even 1400 F. During pulls it can get up to 1100 pretty easy and 1200 - 1300 w/ the chip at about 85mph WOT. During the regen process it commonly can sit at 1100 but usually won't go over about 1325 even at WOT during the cycle. *Edit* **Wanted to add that the EGT's are roughly 300 degrees higher than usual during regen, from what I have noticed that's about the difference it makes. It is normal to see about 900+ on the highway at 65 mph with some light throttle.** I have it set to de-fuel at 1410 and it hasn't done it at that yet, it did once at 1350 F...though I had started from a standstill to WOT on the race setting so...I can maybe see why! Hope this is understandable and helps.

motohed · 09-04-2007, 09:18 PM

just got 07 gmc lmm extra cab short bed 4X4 sunday night. 200 miles on it and i am getting 11-12 mostly city. Upper 12 on the highway. AWESOME TRUCK! traded in my 05 screw F150. NO REGRETS!!!

Billr · 09-04-2007, 10:25 PM

Your experience in town is similar to ours, about 12.5 mpg. However the wife and I just made a 300 mile trip over the Sierra Nevada's and averaged almost 19 mpg driving 60 to 70. Much better than we had hoped. Now if we can just get the towing millage above 13. Our rig, a 22 ft 5th whl, weighs in at just about 7K fully loaded. We'll keep you posted as we venture north next week.

07LMM · 09-05-2007, 07:36 AM

Still about the same here 16-19 City/Highway have 13,500 miles on her..

bigmud44 · 09-06-2007, 11:37 AM

Not very happy with mpg? Had truck for 1 month now, started with 17mpg every time i fill up it gets lower, down to 13.6mpg. Have only 1500 miles on it. I went to the diesel for mpg and not to lose the power i had with the big block. I was getting between 10 and 12
mpg with that. Any help would be great!

Billr · 09-06-2007, 01:21 PM

Is your driving in town or on the road? I have (with my limited experience) experience about 13 mpg in town and about 19 on the road. I drive mine "gently" though and I could see where a heavy foot would reduce it.

jimmarla · 09-06-2007, 02:02 PM

Im still in the same boat with fuel mileage! IT SUX!! PERIOD!! My new LMM last tank got 11.9 pulling light load,where my Cummins that I sold, like an IDIOT, with the same load would get anywhere from 17 to 18 mpg. I really like the 2500hd layout,entire package is nice,but if I would of known the fuel mileage was like this I would have stayed with Cummins! If I knew they would not take me to the cleaners trading mine in, I would still get a Cummins! O well, my bad!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

chuck1975 · 09-06-2007, 09:05 PM

jimmaria, after having a Cummings why did you buy the Dmax? Was it only for the interior / layout that you liked better?
I've always known that the Cummings is always going to give better mpg though Dmax is stating good mpg.
So real life mpg it seems to be Cummings (Dodge), Dmax (Chevy/GMC), IH(Ford)

Also I'm in this same spot (almost) as I'm trying to decide to buy a Dmax to replace my 12 yr old 7.3. I'll still keep the 7.3 for the dirty work, so the Dmax can stay a little nicer for a few more years. Just can't seem to decide, new truck & payments or old truck and parts & labor bills (still way less than monthly payment)

Just a thought as I'm almost in the sae spot
Chuck