2008 Chevy Z-71 Crew Cab - Fuel Economy & Brakes

hutcher1 · January 30, 2008

Hi Guys,

New guy - first post. In December I bought a 2008 Silverado Crew Cab Z-71 4 x 4 half ton . The truck has the 5.3 with AFM, 3.73 gears and 18 inch tires. I have about 2000 miles on it and have run it with an open bed. Will probably put a tonneau cover on - but haven't yet. A couple of questions:

1) The best fuel economy I have gotten out of a tank of mixed city and highway driving is 13.8 mpg. Shouldn't I be doing better than that - with approx 50% being highway driving. I have always driven with a very light foot - so I can't see hard acceleration as affecting MPG. Any thoughts ? Will this improve as the engine breaks in ? Will it improve in warmer weather ? Could my AFM not be working correctly ? Would it improve if I install a tonneau cover ? Is anyone with a similiarly equipped truck doing any better ? Sorry for all the questions but I"m really surprised. The last half ton I had was a 1998 with the old 5.7 and it did better than this.

2) I was a little hesitant about the rear drum brakes. After about a thousand miles they were pulsating when stopping. My dealer turned them for me (also mentioned he had seen this before when the trucks were brand new). Now at 2K they feel like they need turning again. I've always preferred rear disc, and am a little disappointed in the feel of these. Has anyone else had the pulsating problems ? Do they feel better as they break in ?

Again, sorry for all the questions. Anxious to hear your feedback.

Thanks !

grogol · January 30, 2008

I don't have a crew cab, but I have an Extended Cab 2007 Sierra SLT with 5.3 and 3.73, and of course AFM. I get about 16.7 mpg in mixed driving. I would think yours should/could do better. I haven't had any trouble with the brakes front or rear (drums in the rear) in 8,000 miles of driving. Hope things go better for you!

fbachman · January 30, 2008

Hi Guys,

New guy - first post. In December I bought a 2008 Silverado Crew Cab Z-71 4 x 4 half ton . The truck has the 5.3 with AFM, 3.73 gears and 18 inch tires. I have about 2000 miles on it and have run it with an open bed. Will probably put a tonneau cover on - but haven't yet. A couple of questions:

1) The best fuel economy I have gotten out of a tank of mixed city and highway driving is 13.8 mpg. Shouldn't I be doing better than that - with approx 50% being highway driving. I have always driven with a very light foot - so I can't see hard acceleration as affecting MPG. Any thoughts ? Will this improve as the engine breaks in ? Will it improve in warmer weather ? Could my AFM not be working correctly ? Would it improve if I install a tonneau cover ? Is anyone with a similiarly equipped truck doing any better ? Sorry for all the questions but I"m really surprised. The last half ton I had was a 1998 with the old 5.7 and it did better than this.

2) I was a little hesitant about the rear drum brakes. After about a thousand miles they were pulsating when stopping. My dealer turned them for me (also mentioned he had seen this before when the trucks were brand new). Now at 2K they feel like they need turning again. I've always preferred rear disc, and am a little disappointed in the feel of these. Has anyone else had the pulsating problems ? Do they feel better as they break in ?

Again, sorry for all the questions. Anxious to hear your feedback.

Thanks !

1) Shouldn't I be doing better than that --- with winter blend gas, not really. I get about the same with an extended cab Sierra (in the winter). I, too, drive about 50/50 highway/City.

Will this improve as the engine breaks in ? Yeah, probably a little... mine did.

Will it improve in warmer weather ? Yes, see above. In my case, Summer MPG is about 2mpg-3mpg higher than my winter mileage. My summer average: 14-15. My winter average: 12.5-13.5, maybe a LITTLE better on occasion...

Could my AFM not be working correctly ? Possible, but not likely. It's probably fine.

Would it improve if I install a tonneau cover ? Not sure. Someone with a cover will likely chime in soon.

2) Has anyone else had the pulsating problems ?

I haven't as of yet. Got about 8000 on the ODO.

Hope this helps answer some of your ???s.

WELCOME, BTW

EDIT: Just realized you have a crew... little heavier than an EC, as you know.... so... sounds like your MPG is a little better than mine... I think you're ok....

Steveman · January 30, 2008

After 2000 miles your engine should be broken in pretty well. I have 6000 miles on mine and it seems to be getting just a little better mileage then it did when I first got it with 14 miles. I also dont have a crew cab but I have a Ext cab with the 6.6 foot bed, 4x4, and I get normally around 14 MPG. Now I am not too surprised at this because I live in Dallas and their is always stop and go traffic. What I try to do is watch the little AFM indicator on the DIC so I can tell when its in V4 mode. Everytime I can, I set the cruise control and let the engine work in V4 mode. The best mileage I have gotten was one time going to a friends farm and I got 18 MPG. Now what is really surprising about that is I had my 600 pound ATV in the bed. So, I would recommend trying to use cruise control as much as possible or just watch the AFM indicator and try to use the V4 mode as much as possible. One thing that really kills your mileage is hills, so if you live in a area with a lot of hills, forget about getting good mileage. I cant really comment too much on the brakes, mine have been trouble free so far except they do squeek once in awhile on cold mornings but that usually goes away after about a minute.

2004GMC1500CC · January 30, 2008

Hi Guys,

New guy - first post. In December I bought a 2008 Silverado Crew Cab Z-71 4 x 4 half ton . The truck has the 5.3 with AFM, 3.73 gears and 18 inch tires. I have about 2000 miles on it and have run it with an open bed. Will probably put a tonneau cover on - but haven't yet. A couple of questions:

1) The best fuel economy I have gotten out of a tank of mixed city and highway driving is 13.8 mpg. Shouldn't I be doing better than that - with approx 50% being highway driving. I have always driven with a very light foot - so I can't see hard acceleration as affecting MPG. Any thoughts ? Will this improve as the engine breaks in ? Will it improve in warmer weather ? Could my AFM not be working correctly ? Would it improve if I install a tonneau cover ? Is anyone with a similiarly equipped truck doing any better ? Sorry for all the questions but I"m really surprised. The last half ton I had was a 1998 with the old 5.7 and it did better than this.

2) I was a little hesitant about the rear drum brakes. After about a thousand miles they were pulsating when stopping. My dealer turned them for me (also mentioned he had seen this before when the trucks were brand new). Now at 2K they feel like they need turning again. I've always preferred rear disc, and am a little disappointed in the feel of these. Has anyone else had the pulsating problems ? Do they feel better as they break in ?

Again, sorry for all the questions. Anxious to hear your feedback.

Thanks !

wonder if those rear brakes may be dragging?

pm26 · January 30, 2008

I have an '06 crew cab Z71 with the same engine and gear ratio, and no AFM. The city mileage is around 15 MPG. I live in Florida and Ii do not think they sell any winter blend fuel here.

Pulsing brakes is something new or '07 on NBS, as I have not heard of this issue for the '06 model.

7500 miles on mine and besides some grooving on the right front rotor, no brake problems.

You may want to try different octane gas to see if the mileage improves. Also stay away from no name brand gas stations. Run a bottle of Chevron Techron injector cleaner with about 8 gallons of fuel through the tank about every 3k miles.

RCman · January 30, 2008

[snip] and 18 inch tires. [/snip]

Well there is your problem!

To answer your questions:

1) Yes, mileage should improve both after break in and in warmer weather.

2) Brakes should not be doing that at all. Request the dealer replace the drums, not turn them (you loose life of your brand new brakes)

slomo007 · January 30, 2008

I've got a NBS crew cab also, but 2wd with the 18" wheels and 3.42 rear end.

I bought in late September and my initial mileage was about 17-18 with mostly city driving (live north of Fort Worth and drive downtown everyday for work). I am VERY light on the throttle though, mostly because I get to work early and if there's one thing that doesn't appeal to me, it's hot rodding around town before I've had morning caffeine.

But, lately my mileage has been 16.5 or so, same driving patterns. I don't think the fuel has changed (no need for winter blend fuel here), but it's obviously colder outside and therefore the truck takes longer to warm up anytime I go anywhere. The longer the engine is "warming up" the worse mileage it gets.

Bottom line, I wouldn't worry about the mileage until you get a chance to see what it can do in warm weather. My guess is you'll get 15+ which is about all you can hope for with mostly city driving, 4x4, and the 3.73 gears.

motoxxx · January 30, 2008

I get around 15 mpg on my 2007 5.3 with AFM. Did I mention AFM sucks...it's really annoying when you can feel it go back and forth twenty times in one minute. I’m thinking about programming the AFM out of my life...along with a little torque management. Running 305/35/24 and that could be contributing to my gas mileage a little too.

My rear brakes are pulsating too and have been for a while. Truck goes to the dealer Monday to get brakes fixed and annoying vibration at 50-60 mph. Truck has about 4500 miles.

Rocco715 · January 30, 2008

I get around 15 mpg on my 2007 5.3 with AFM. Did I mention AFM sucks...it's really annoying when you can feel it go back and forth twenty times in one minute. I'm thinking about programming the AFM out of my life...along with a little torque management. Running 305/35/24 and that could be contributing to my gas mileage a little too.

My rear brakes are pulsating too and have been for a while. Truck goes to the dealer Monday to get brakes fixed and annoying vibration at 50-60 mph. Truck has about 4500 miles.

You feel your brakes pulsating becuase a 24 inch rotational mass take much more to stop than a 17,18, or 20 and if you feel a vibration you rims probably aren't balanced right.

and back to the main topic your not going to see the full potential of fuel economy until you've got some more mileage. Your truck isn't even completely broken in.

pm26 · January 30, 2008

Did I mention AFM sucks...it's really annoying when you can feel it go back and forth twenty times in one minute.

This is why I bought an '06 truck. I knew this AFM crap was coming soon.

motoxxx · January 30, 2008

"You feel your brakes pulsating becuase a 24 inch rotational mass take much more to stop than a 17,18, or 20 and if you feel a vibration you rims probably aren't balanced right." Quote

? Um...no

I said my rear drums are pulsating. I did not say my brakes are pulsating because I have heavy wheels that take longer to slow down thus I feel a vibration because my rims are out of balance. Again, my rear brake drums are pulsating and need to be turned or replaced.

My wheels have been road force balanced and I have new power slot rotors up front. Any other predictions because I think the rear drums are the issue.

Not to mention, I have run my stock wheels and it made no difference.

07BlueSierra · January 30, 2008

As someone who seems to have more miles than most on my NBS I can say that I get 15.5 mpg no matter what. I am in the truck a lot on 2 lane roads at about 60 but here in SC we drive pretty briskly on the interstate at about 80. This winter I have let it warm the cabin before driving off most every morning and I am still getting 15.5

Specs:

2007 Sierra Crew Z71 4x4

5.3 AFM w/o flex

16k miles - owned since 8/07