Duramax LBZ MPG

[MAGhunter]

So I've had my 06' Silverado 3500 crew cab Duramax LBZ 4x4 for about 6 months.  I have a 6" lift and running 37" on it.  It also has an AFE cleaner and Banks dual exhaust...........My MPG sucks!!!  I have been averaging about 12-13 MPG.  I mostly drive the freeway about 50 miles a day.  I do not have a tuner yet and am hesitating to buy one for my warantee purposes. 

What is the DEAL??

Any thoughts. 

[Dhoey07]

I have an 06 lbz with a 7" lift and 35's and average 15.5 mpg's combined unadjusted for the tires.  I have an intake, exhaust and a tuner. So maybe with the bigger tires and no tuner, 13 might be normal

[Elkaholic daWg]

 Has your computer been adjusted, since stock it was figuring you are running 29 inch tires? if not you might want to add about 29% of what your dash readout says (and to your trip odometer)

[Rick]

The deal is big heavy tires with a lot of rolling resistance.

You have two choices,look cool while getting crappy mileage,or take it back to stock and gain about 6mpg.

[beaslayer6]

I had a 06 lbz with a 6 lift and 35 it got 17-18 all the time but the dam thing drove and towed like hell.. needless to say no more duramaxs..

[Killmore]

I have the 06 lbz  3/4 ton, with 285 tires and a stock tune I will get 16 mpg on the freeway and with a diablo tune with the tow tune installed I can get 19-20 mpg. Wouldn't you be out of the warrantee?

[JohnVH]

1) dont trust the overhead Lie O Meter
2) GPS to see how far off your speedo is
3) hand calculate your MPG

That said, with big lift and big tires, its not an economy car anymore, haha.

My 05 cummins on 35's gets 16-18 around town, and about 22 unloaded highway, my old 05 duramax got way worse

[elkinrutdrivemenuts]

You are running a 6.6L 8 cyl Duramax.  16 to 18 with stock tires and stock motor is average.  Even with tuning, intake, exhaust it will be damn near impossible to get 16-18 mpg with those big tires.  Sorry man, we get calls like that every day, your getting the mpg your going to get with that set up. 
I had an LB7 with 33's and 14mpg was good.  I had EFI live, intake, upgraded down pipe, 4 in exhaust, and a built tranny.  Running 500hp was cool, but once I started playing with it and threw bigger tires on, MPG went from 16-18 down to 14 on the freeway on a good day.  During the winter, 11-12 was average. 

[Elkaholic daWg]

 O5 here with 255 16ss which are as tall as 285's but not as wide for snow, and clearance since all I did was torsion keys for minimal lift and level
 Stock wears 245's at 29"
                   255s are 32"    3 inches is 10% + of stock so I ADD 10 % to odometer (verified by highway mileage markers) traveling speed on speedo, and lie o meter on dash working out to about 19.4  ALL  driving last 12,000 miles since changing tire size. Towing or not.......highway or woods.........idling to keep the other half warm

[cohoho]

Sold my 06 Duramax recently, but at 289,000 I was getting a consistent 16-19mpg from new to the time I sold it with 285 tires...  With 37" tires your doing great at 12 mpg...  Not much option but to down size tires..