LB7: Fuel mileage

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whitemax03

New member
Jul 4, 2010
19
0
0
winnsboro louisiana
Hey guys im kinda new hear and not sure if i put this in the right spot. Sry if its in wrng place.
So hear goes ive got a 03 ext cab duramax running 35s on 18s truck is 100% stock except for the topkick ecm and fcim and im getn horrible fuel mileage. Like about 12mpg at the best. What can i do to help increase the mileage.

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THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
43
48
43
ZEPHYRHILLS, FL
Why does it have a topkick ECM in it? I would go back to a regular truck tune as it will have a MUCh better fuel curve in it for driving unloaded. With your tires though, if you have stock gears I wouldn't expect much for milage. I just had a guy here with an LMM(08) with 35's, and all he is getting is 10-11 empty or loaded. them big tires look good, but with stock gears KILL your milage. Put in a stock tune with optimized timing(EFILIVE, and yes it will work on 4500/5500 tunes), and some 4.56 gears if you want to keep the bigger tires.
 
whitelmmmax

whitelmmmax

Smaller than stock
Jul 26, 2011
693
0
0
36
lake charles, la
THEFERMANATOR said:
Why does it have a topkick ECM in it? I would go back to a regular truck tune as it will have a MUCh better fuel curve in it for driving unloaded. With your tires though, if you have stock gears I wouldn't expect much for milage. I just had a guy here with an LMM(08) with 35's, and all he is getting is 10-11 empty or loaded. them big tires look good, but with stock gears KILL your milage. Put in a stock tune with optimized timing(EFILIVE, and yes it will work on 4500/5500 tunes), and some 4.56 gears if you want to keep the bigger tires.
Click to expand...

X2 on the truck ECM. Before the triples I was getting 15 in town and 19 on interstate with 35s.
 
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whitemax03

New member
Jul 4, 2010
19
0
0
winnsboro louisiana
Efi live sounds good. Idk if ther is anybody close to the northeast louisiana area that does it or not. How do i find a dealer for it. The truck was a border patrol truck and the top kick ecm was in the truck when i bought it but i wasnt aware that it was in there until i tried to program it. Ive got 4.11s in my trucl now and the fuel mileage really wasnt any different with the stock tires and wheels.
If i was to get efi live can i still tow with it. I occasionally pull a 40ft gooseneck loaded down with 4wheelers and sxs. Prolly in the 12000lb range far as weight goes.

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dbev24

dbev24

Member
Oct 27, 2011
390
0
16
Darlington pa
whitemax03 said:
Efi live sounds good. Idk if ther is anybody close to the northeast louisiana area that does it or not. How do i find a dealer for it. The truck was a border patrol truck and the top kick ecm was in the truck when i bought it but i wasnt aware that it was in there until i tried to program it. Ive got 4.11s in my trucl now and the fuel mileage really wasnt any different with the stock tires and wheels.
If i was to get efi live can i still tow with it. I occasionally pull a 40ft gooseneck loaded down with 4wheelers and sxs. Prolly in the 12000lb range far as weight goes.

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Click to expand...

Yea u can still tow. Put a dsp5 and get tow tunes and fuel economy tunes. Just look at some vendors on here they will hook u up
 
TheBac

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,528
1,802
113
Mid Michigan
Talk to member "bluessmax". His name is Kory. IIRC, he lives in Louisiana and does tuning.
 
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