Decided to sell the 04 denali 6.0 - Im going to buy a used silverado or sierra and want to know the best one to get for fuel milage. I ...

Im going to buy a used silverado or sierra and want to know the best one to get for fuel milage. I am going to get the 5.3 because I tow trailers and go up mountains often. Does the gear ratio make a difference or what? we have an 09 silverado crew cab that wil get 19 highway and has the AFM...I am going to make sure my new truck as AFM but what else should I Make sure it has? it has to be a 4wd and prefer z71..whats the difference in the z71 and standard? Thanks guys!

Z71 has the beefed up suspension, extra skid plates, rear gov lock limited slip differential, more aggressive shocks (stiffer). Not 100% but I think it has better tires as well. As for MPG I wouldn't go higher then 5.3 unless you need the torque and HP.

Also, from a gear ratio standpoint:
3.42 are really good for towing, but 3.08 will give better MPG. If you are doing mountain towing, though, you will not like the 3.08 at all. Go with 3.42.

EKinMN wrote:Also, from a gear ratio standpoint:
3.42 are really good for towing, but 3.08 will give better MPG. If you are doing mountain towing, though, you will not like the 3.08 at all. Go with 3.42.

What do you think the difference in MPG will be?

It depends on how heavy your foot is. I have the 3.42, and get in the upper teens (18-ish). You might add a point, or 1.5 to that, but no more. No one is averaging over 20 that I am aware of.
The key is being light on the pedal, and keeping the RPM's below 2000 when not towing.

gotcha. Now I know some of the sierras say "all terrain" such as yours on the side...whats the difference? I do go off road so id like the z71 and all terrain if possible but when you get the z71 do you automatically get the all terrain badge?

Nope. All Terrain is a separate package. it has some interior differences (like the brushed aluminum dash panels), and it has skid plates (that may be standard on the Z71....I do not remember). Mine also has the Z71 suspension.
But you can get the Z71 without the All Terrain, if you want to.

having brushed aluminum dash panels really helps it off road I'm told!! just kidding..but thats so dumb to have that as part of an "all terrain" package.. is active fuel management standard? and does it really help much?

I don't know what the AFM does overall. It's standard on all 5.3L engines now, so it's really not an option.
I have only been off road once, and I got to tell ya, I would never have made it off the trail without my aluminum dash! It helps in deep snow, too.
There are other things that are part of the all terrain...I just cannot name them off the top.

EKinMN wrote:Also, from a gear ratio standpoint:
3.42 are really good for towing, but 3.08 will give better MPG. If you are doing mountain towing, though, you will not like the 3.08 at all. Go with 3.42.

I thinks it's debatable whether the 3.08 will show better mpg. In many cases could possibly be worse such as in terrains that will cause frequent downshifting.