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Duramax Fifth Generation: 2011-2016 (LML) Discuss the fifth generation (2011-2016) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 05-20-2017, 05:33 PM   #1 (permalink)
lynn1130
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Fuel Mileage

I have seen a few threads here on the LML where people were banging on their poor fuel mileage. I had to put a word in here about what I have found.

This is my second Duramax and the 04 did very well on mileage so I was concerned that the 14 with all of the emissions crap would have crappy mileage. I found that it won't quite reach the 04 but it ain't bad.

I made a 2000+ mile round trip to turkey hunt in Kansas. I hand calculated mileage for the first couple of tanks but when I found that my math was within tenths of what the truck was telling me it was getting I stopped doing it by hand. The truck averaged 20.4 mpg going and 19.6 coming. Generally there are tailwinds going and head winds coming home so 20 even for the trip. I generally was at 80 mph on the Interstates and 70+ on the back roads.

The 04 on those trips would be about 24 mph average.

A little different story pulling the toy-hauler last week camping/hunting. It is all uphill going and all downhill coming. Going up was just under 7 and coming down was almost 10 (still a few big mountains to climb but most of it is downhill).

So, overall I am happy. I was a little worried when I was reading threads where people were only getting 15.

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Old 05-20-2017, 10:41 PM   #2 (permalink)
ktmrfs
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my 15.5 gets better highway mileage than my 04.5 did. by about 2mpg on a long trip, I can push near 20 on the 15, while the 04.5 was around 18.

But I've heard the 04 LB7 got better mileage highway then the 04.5 LLY

Now towing, can't say as there is any difference.

In town, again, both are about the same.

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Last edited by ktmrfs; 05-20-2017 at 10:42 PM.
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Old 05-21-2017, 01:50 PM   #3 (permalink)
GuyN
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Around town and some country roads to and from work I get 13-15 MPG, not towing.
Towing my 5th wheel I average about 12 MPG, freeways and backroads combined.
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Old 05-21-2017, 03:28 PM   #4 (permalink)
drperry
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I'm getting about 9MPG empty, highway mileage, lol. Maybe up to 10 now.

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Old 05-29-2017, 07:10 PM   #5 (permalink)
zetan
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2015 Chevy Silverado 2500HD, 8700lbs, 550 miles avg 20.1mpg
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Old 06-07-2017, 12:48 AM   #6 (permalink)
jeffmarsh750
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12.7 on a 2016 and that is country driving, empty and some freeway. Tripometer is at 5000 for that read. My old cummins farm dually 12 valve with 300k still gets over 15mpg and we drive it hard. We are going to race them because I think it will beat the LML to about 65mph and if I could get the converter on in 2nd I know it would smoke the new D max. #LMLsucks !
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Old 06-07-2017, 01:24 AM   #7 (permalink)
Randy G
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My 2015 2500HD crew cab 2WD on the freeway from CA to Oregon and back posted slightly over 20 mpg.
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Old 06-07-2017, 08:31 AM   #8 (permalink)
briano
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highway/extended trips do not hurt the mileage at all, it helps clean the DPF, however, city driving, stop and go...quickly kills your mileage and increases regens, etc. I do 90% city driving and had never gotten barely over 300 miles a tank. Every tank since deleting, has been 400+, filling up once a month instead of twice a month. love it!
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Old 06-07-2017, 10:12 AM   #9 (permalink)
maxinDixon
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The last 400 miles my DIC is showing 20.4. I used it for long trips mostly. My regens are usually around 700 mile intervals lately. Got 13,300 miles on the truck.
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Old 06-07-2017, 01:25 PM   #10 (permalink)
drperry
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Quote:
Originally Posted by jeffmarsh750 View Post
12.7 on a 2016 and that is country driving, empty and some freeway. Tripometer is at 5000 for that read. My old cummins farm dually 12 valve with 300k still gets over 15mpg and we drive it hard. We are going to race them because I think it will beat the LML to about 65mph and if I could get the converter on in 2nd I know it would smoke the new D max. #LMLsucks !
Unless you have that old 12V modded a fair bit... The only way it'll touch your LML, is if something is wrong with it, lol

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