07.5+ LMM Duramax PowertrainDiscussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission Ect
I suspect that fuel temperature (density) is a major culprit as it can vary by almost 20%. With fuel prices @ $4, a warm fuel temperature can cost you as much as 80 cents a gallon.
Bill
Sorry for the late response to this but I have a dumb question. I'm trying to make sense of your statement. Isn't a "warmer fuel" a less dense liquid which means you are getting less for your money? So you might actually be paying $5/gal for that "warmer fuel".
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'06 LBZ
18,000 miles to date
PPE hot +2 e.t (Jan 22,2008) sold on Jul 29,2008, EFILive (July 29,2008), egr block plate,pyrometer and boost gauges,Line-X bedliner, power step, matching door handles (Escalade), billet grille, clear braw to prevent rock chips, led tail lights, high intensity headlamps, two 10" subs, rockford fosgate 1000w amp for subs 5w-40 synthetic engine (Feb.17,2008), 75w-90 synthetic differentials (Feb.17, 2008), fuel additive (Feb.23, 2008)
Millage Update
We have now traveled on this trip 2438 miles. From Vacaville, CA to Austin, TX. There are a couple of interesting points I would like to share. The first is the average millage over the entire distance which was 11.51. This is the hand calculated number and the actual number of gallons placed in the tanks. The DIC numbers are, for the same number of gallons placed in the tanks, 194.1 used for a millage of 12.56. This is slightly over 1 mpg difference over a distance of approximately 2500 miles. The average speed was 60 mph although it doesn't seem to make much difference to do 65. Most was in the western mountains although the last 600 or so was in a flat, western Texas. We have also noted that our towing millage is just about the same as our "in town" millage. The truck is stock LTZ with a transferflow fuel aftermarket tank. The only time we paid attention to how full the tanks became was the last time when everything was totaled up and calculated. We topped off the tanks (it took 3 credit cards) and made sure there was no "foam". Were pretty sure that by using this large a base count that there was little "foam" error. The temperature of the fuel is another issue but for our purposes it makes little practical difference. The tires are stock 265 r70/17.
Bill
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Billr
2K8 Silverado 2500 HD LTZ 4x4 Access Cab Garmin GPS, Full Towing Package, Integrated brake controler, Camper mirrors, Skid plates, line-x, Nerf bars, Reese Slider, an extra 30 gallons, and an empty bank account.
These are hand calculated #'s. My DIC is consistently shows mileage to be 5-6% better than it actually is.
Over a distance of approximately 2500 miles our DIC understated the # of gallons used and inflated our MPG by 1.1 mpg when towing a 9000lb 5th wheel. A 9% difference if my math is correct.
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Billr
2K8 Silverado 2500 HD LTZ 4x4 Access Cab Garmin GPS, Full Towing Package, Integrated brake controler, Camper mirrors, Skid plates, line-x, Nerf bars, Reese Slider, an extra 30 gallons, and an empty bank account.
I've got a new 08 LMM and seem to be getting about 10-11MPG towing my 37ft 5th wheel with 4 slideouts guessing about 13,000 lbs. Getting ready to put a S&B cold air intake to see how that helps. Getting about 18+ highway at 70MPH, 14-16MPG in town depending on how well I stay out of that damn accelerator pedal.
Sorry for the late response to this but I have a dumb question. I'm trying to make sense of your statement. Isn't a "warmer fuel" a less dense liquid which means you are getting less for your money? So you might actually be paying $5/gal for that "warmer fuel".
Absolutely... Diesel can expand from 6.2 lbs per gallon to almost 7. Do the math. That is a factor of almost 15% or 65 cents a gallon for really warm fuel. When fuel was much cheaper this was so not much of an issue. I think fuel compensated delivery pumps ought to be the law. This is one area where I DEFINITELY agree that we are being ripped off. The DEALERs get temperature compensated fuel. Any idea why we don't?
When Commercial/military airplanes calculate fuel load, its done in pounds, not gallons. Diesel can expand far more than enough to be a "safety of flight" issue. Hot/warm fuel doesn't get you as far. A significant loss of "btu's".
Bill
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Billr
2K8 Silverado 2500 HD LTZ 4x4 Access Cab Garmin GPS, Full Towing Package, Integrated brake controler, Camper mirrors, Skid plates, line-x, Nerf bars, Reese Slider, an extra 30 gallons, and an empty bank account.
Hey - I am new to the forum and a new diesel owner. I took my 08 GMC Xcab longbed 4x4 to the coast (Newport Oregon) and while keeping the revs around 1500 rpm I was rewarded with 21.7 mpg. 500 miles on the truck.
Thats hard to accept....You may be getting 21 mpg but my 08 3500 4x4 crewcab dually is only getting 13 mpg tops no matter how I drive it.....it sucks>>>>fuel
Ron
Yea dude I was pleasantly surprised. This is driving up/down the small hills along the coast, stopping at different beaches, you know, screwing off and enjoying the scenery. I rarely drove over 65.
The only planned mods are a B&W companion 18k 5th wheel hitch that will be installed on Thursday to tow my cat house.
The hitch is really cool!
Maybe when I get farther into my warrenty I will consider turbo back exhaust and a tuner.
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Billr
Fuel Density 
Linear Mode
