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Discussion Starter · #1 ·
I recently bought my LLY not knowing much about diesel trucks. People around the house are getting better fuel mileage than me. I get around 14 mpg know. When i first bought the truck i was getting roughly 18-19mpg. I brought it to the shop several times, but they made me feel stupid. It was blowing white and grey smoke when i gassed on it to pass cars and the fuel smelled real rich out the exhaust. I took out my programmer and it doesent smell that bad anymore. I just got it back from the shop on a recall on gauage cluster and it seems to run better, but fuel mileage stinks. I would like any suggestions from anyone. Thanks
 

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Programmer dumps in more fuel for more pwoer.. hense the rich smell.
14-15 mpg is what I have gotten on everyday driving since I bought my truck, it does better on long highway trips, if I keep it under 65 I can pull almost 20 mpg.
 

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I'm getting 14.1 ....................but i haven't used a full tank yet , That was the 1st owners milage
 

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I am getting 18 average, around 17 in town and 19-20 on hwy. I do have alot of after market work though.
 

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Mine gets 13-17 around town, 17-20 on highway deadheading, and 10 with 5th wheel trailer on highway. I lost one mpg when the computer was reflashed to stop smoking problem and another mpg when ultra-low sulfur fuel was introduced.

Before I bought my truck, a lot of Durmax owner sure lied to me about their mileage! Now that they know that I know, most tell a more truthful story!

I must say that I thing the LLY has the poorest fuel economy of all the DMaxes.
 

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Seems like a small price to pay with all the torque and horses under the hood. I get 13.5 to 15mpg in my 3500 and never got any better out of the 1/2 ton I use to drive. I sure can tell the difference when I need to get the job done though!! Mine seem to just keep giving and giving when I need it to, so the trade off is small to me. I added a Juice with Attitude Module to my ride and can get 14 to 20 depends on how far my foot is in it,but the power is un real. Get more Black smoke now but addition of cold air intake should solve that and make all that wasted fuel go to work. I`m told that will help mileage some too.
 

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avg. 15-18. but I drive pretty fast on the freeway. I noticed if I keep it at 2k rpm or lower when cruising, it get's best mileage. I've seen 1-2mpg drop from just 300rpm over 2k. for extended time periods.
 

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Are you hand calculating your mileage. The hypertech is a very safe tuner and you should be getting better mileage with it. When was the last time you changed you fuel filter? Is it getting better mileage after the programmer was downloaded?
 

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Discussion Starter · #10 ·
I changed my fuel filter about 3K and also had oil changed and tranny serviced. Not to cheap to do all that. This morning i noticed that my fan would kick on and off every few seconds. I'm wondering if it 's not staying on all the time i'm driving. The engine was cold this morning when i noticed. I really did not notice a difference in milagr wit or without Hypertech in.
 

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Is your programer set for the right tire size ?? I see differences between 245s and 265s. With same set up on programer. Just curious !!!
 
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Steve,

Things to remember:
  • Tire pressure - keep it at 65/80, or 80/80. The higher tire pressure, the less rolling resistance... the better the fuel economy.
  • Stock tires look puny, but they max out on the fuel economy. Bigger tires and lift kits look great and can enhance off-road capabilities, but all at the cost of fuel mileage.
  • TxC's CAI with a good clean stock filter will do everything you ever need for cold air, and will add mpg's (added 2+ to my truck) for all of $60. Best money you can spend.
  • Fuel additives - I use Power Service. Some claim as much as 2 mpg's; I see less than that. YMMV...
  • I don't know Hypertech's tuners; I have a Predator. Predator has an economy tune - +65 hp - that added a couple mpg's to my truck.
  • Blocking the EGR/reroute the PCV will at the least keep you from dumping sludge back into your intake. I've not been able to tell, but some claim mileage improvements.
  • Custom exhaust (4"), especially w/cat delete, is supposed to net you additional hp and theoretically additional mpg's (if you can keep yer foot out of it). Besides gauges, this is my next step.
  • Bed cover - the jury is still out on mine, but again... theoretically, a good bed cover should improve aerodynamics thus mpg's. I'm beginning to believe that unless you get a rigid one, you won't gain anything. :(
  • Driving habits - you can do all of the above and more and still drive like a nut and get lousy mileage. Lots of tips out here and in other places on the 'net. 2k rpm's, learn to coast, don't drive up to stop signs/lights, etc.
You can see my mods below. When I keep my foot light on the skinny pedal, I get 15-16 in town and 22+ unloaded on the highway. My goal is still 25 mpg on the highway; I'm not there yet, but I am convinced it is achievable. Good luck!
 

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"avg. 15-18. but I drive pretty fast on the freeway. I noticed if I keep it at 2k rpm or lower when cruising, it get's best mileage. I've seen 1-2mpg drop from just 300rpm over 2k. for extended time periods"

Ditto what TP said above in quotes...

I'v driven my 2005 2500 2wd silverado 53,000 miles since I bought it new in July 2005, 15-18 best discribes my fuel milage...

When I tow my #5000 racecar on an open trailer to go racing, 13-14 is the average, I am sure if I slowed down to say 60 mph, it would get 15 mpg towing, it's just too easy to cruise in the 65-70 mph range in this truck...

My old 1500 gas truck got 10 mpg towing, on a good day, and it was gutless. It got 17 normal driving. It could not do near what the Duramax is capable of, and the Duramax weights about #2000 more than the old gas truck. So the Duramax wins against the old gastruck, hands down, no doubt...

My neighbor just bought a 2003 Dodge 3/4 ton crew cab 2wd with the cummins inline six deisel...

He always mentions his 18-20 MPG or whatever mpg he gets, I get tired of hearing it...

If I have to drive a Dodge to get the cummins inline six cylinder deisel, to get better gas milage, then I guess I'm stuck with 15-18 MPG, cause I'm not going to drive a Dodge, period...
 
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My buddy just bought a new Dodge Cummins and he's getting terrible fuel economy. He's seeing 12-14 mpg tops. He had an older one that got pretty good mileage, but his new one absolutely sucks fuel.

YMMV...
 

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Can`t Hammer Cummins too much.... They are in American Trucks. What psss me off is when Toyota and Nissan Drivers want to compare what they drive to my TRUCK !!!!!!
If you want to get 18-20 Mpgs fine. If you want a Real American Power Plant that "Can and Will " get the job done there is none better on the road than Duramax. Just how much can you get fron a rice burner anyway ? Let alone ridding in one. I`d rather ride a bicycle than be cramped into one of those things.Silverado,Ford,Dodge, I`ll take any of them, but rather drive a CHEVY !!! Besides I can get better mileage with Mods and a little driving sense. Plus every Mod you put on these babies alos brings on the Horses and tons of torque.. Sorry guys but not sorry in a way too...
 

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Tom2500HD If your Max is so bad and you think other wise all you need to do is drive a 2500hd gasser and get back at us..........Then you'll know what milage is all about are company has three and they never get above 12mpg on there best day. other wise ther 10 and 11 at best. And my 05 must be poor than cuz i get 26.4 out on the highway If as you say the LLY's are the poorest i wonder just how good everybody else really is?
 

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The profit stays right here in the US and helps boost the econmy here instead of going stright sea's. It is just like the a Honda plant here in the US, sure they employ some Americans but at the end of the day the majority of the profit goes right over sea's.


Back to the topic at hand, I get about 25mpg on the highway and 18ish in the city. Very happy with the milage. My old 99 s-10 4x4 got 15mpg and was only 3,200lbs...
 

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Light foot on the gas and keep it at or under 2000 rpm. I could easily get 3-4 mpg less by driving harder. Also, the defroster will run the A/C compressor and drop the mileage .5-.9 mpg. I'm getting 18 right now and it's damn cold out.
 

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Durmax fuel mileage

I just got the average fuel mileage off of my '05 LLY, and driving city/highway stop and go between 15 and 60mph when I got home I had averaged 20.9 MPG, considering I have a 6" lift and 325/70-17's I think I am doing pretty good. I Have the banks six gun system with Banks Monster exh, and Intake running amsoil 15w-40 with duel filter bypass. I drove with my Banks on setting 6 driving civilized, with the banks on setting 2 on the same trip I averaged 18.8 last week. The Duramax obviously has the potential to get great mileage, I think how far your foot is in the throttle is the main factor.
Also in the next few days, I will be installing a PPE EGR Delete intake manifold, and switching my transmission fluid over to amsoil torque drive, and I will re clock it and see if there is any noticeable difference
 
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