GM 5.3 gas mileage

   / GM 5.3 gas mileage #1  

deerefan

Veteran Member
Joined
Aug 23, 2005
Messages
2,102
Location
louisiana
Tractor
1952 8N, 2005 JD 5103
I bought a 2011 Z71 4x4 ext cab in December. It has the tow package and 3.42 gears with the 6 spd auto. I have about 5500 miles on it and am averaging 15.8 mpg hand calculated. I find this rather disappointing considering my 97 F150 4x4 ext cab with the 4.6, 4 spd auto and 3.55 gears get 15 flat. Here we are 14 years later and light years ahead in technology and the mileage is basically the same. I can't call GM a liar as it states 15-21 mpg on the sticker and I am getting 15.8 (the computer mpg says 16.3 avg). For comparison, my father has a 2010 avalanche, 2wd 3.42 gears and he is seeing 18-19 mpg. I drive normally, not lead footed. Another thing I noticed is at 62 mph, I am turning the same rpm as my ford. Weird considering my trans has 2 more gears than the ford. Anyone have the same truck? What mpg are you getting?
 
   / GM 5.3 gas mileage #2  
I have a 09 Z71 suburban 4x4 with same engine transmission and gearing. I average about 17.5 on the computer over 40K on the truck.

HS
 
   / GM 5.3 gas mileage #3  
Reading your facts is astounding.. My 1973 Chevy 307/ {350 later} had 3 on tree and 3.40 gear. It pulled 15mpg and 14 mpg respectively. Now does your 6 speed include overdrive? Seems like something is missing here, other than does your 4x4 , become a 2wd, or is it maintained ? Btw my Son drives a 97 ford 4x4 same as yours and it does the same mpg with a whole lot of miles on it..
 
   / GM 5.3 gas mileage #4  
That seems off. I had the exact same truck as you except it was a 2005 which only had the 4 spd auto. In the summer I always averaged 17.5 mpg mixed driving, winter dropped usually 2 mpg with the different fuel. I would think you should average 18 to 19 mpg. Highway the truck was always 19-20 mpg up to about 75 mpg, and didn't drop too much doing 85 or so. This was all hand calculated.
 
   / GM 5.3 gas mileage #5  
I bought a 2011 Z71 4x4 ext cab in December. It has the tow package and 3.42 gears with the 6 spd auto. I have about 5500 miles on it and am averaging 15.8 mpg hand calculated. I find this rather disappointing considering my 97 F150 4x4 ext cab with the 4.6, 4 spd auto and 3.55 gears get 15 flat. Here we are 14 years later and light years ahead in technology and the mileage is basically the same. I can't call GM a liar as it states 15-21 mpg on the sticker and I am getting 15.8 (the computer mpg says 16.3 avg). For comparison, my father has a 2010 avalanche, 2wd 3.42 gears and he is seeing 18-19 mpg. I drive normally, not lead footed. Another thing I noticed is at 62 mph, I am turning the same rpm as my ford. Weird considering my trans has 2 more gears than the ford. Anyone have the same truck? What mpg are you getting?

I had an 03 with the 5.3. Not sure on the tranny, 4speed? maybe 5?? and I could get around 16MPG like you. Loaded with a trailer and tractor @ ~6500lbs, I would only get 9-10MPG.

But you are right, I dont think we are getting anywhere with the mileage on these trucks. A lot of it is emissions BS, but I think we could still do better and we are not.

Dad had a 1985 chevy K20. 3/4 ton, 4wd, 3-speed w/ granny, 350 carbureted. And he could get 15MPG. He was utterly disappointed when he traded it (many years ago) for a 1998 dodge w/360 and couldnt do any better. And then again, when he got a 2005 dodge w/hemi and still...14-15MPG. It seems in almost 30 years, there has been NO improvement to MPG. Even with double the gears in the tranny:confused2:
 
   / GM 5.3 gas mileage #6  
Ld1, Yes there has been a bunch of different engines, some of the guys here has gone to nearly straight exhaust and not cats, still not getting the advertized mileage.. I had headers and turbo exhaust on my old 73 and never even raised it 1 mpg. But I do not see how these guys feed those Hemis...?I read comsumer reports and they raised 9 mpg in city?
 
   / GM 5.3 gas mileage #7  
Here 2007 NBS 5.3 w/ 3.73 & 4 spd. auto gets approx. 15-16mpg average and I have gotten as high as 20 highway alone. In 121,000 miles the average on the computer is 16.9mpg. Almost exactly the same as all models I've had w/ 5.3 eng. regardless of rear end ratio.
 
   / GM 5.3 gas mileage #8  
It takes X amount of horsepower to push a 4x4 through the air at any given speed. That required HP is directly proportional to the amount of fuel you use.

Doesn't matter what gearing, what engine, whatever.....

Speed is the enemy for fuel economy with these trucks. Even my Explorer will touch 30mpg if I stay under 50mph, with no head wind, warm air, etc....

Your consumption will go up exponentially with your speed. It is not linear.
 
   / GM 5.3 gas mileage #9  
maybe to new of a truck mine gets 20-22 hwy (1957 chevy 3 speed overdrive and a 342 rear gear) I think I will keep it but my 2002 gmc 4.8 get around 20 not much dif in all those years.
 
   / GM 5.3 gas mileage #10  
I average around 16mpg with mixed driving..2011 GMC 6.2 6sp 3:42 4x4. I run it pretty hard though, 70+ mph going to work.

On the highway, taking it easy, I can get 19-20 depending.
 
 
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