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Discussion Starter · #1 ·
So i had my truck for about two months now. I bought it as it currently is. Lifted with 35" tires. My MPGs have been pretty bad. On regular fuel i get a constant 10.6 mpg. On premium fuel i get about 11.6 to 12. I know it was going to be bad gas mileage for the way the truck sits but this bad? Or is this normal? I know that living in the NW probably does not help either with hills everywhere especially where i live. Whats a good way to improve it? I've been looking into getting a tuner soon. Truck already has a K&N air filter and no-name dual exhaust. Any help or suggestions is appreciated.
 

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I've got a bone stock 2009 with the 4.8 and MPG's are horrible.
Mine has the Z85 suspension package with 3.23 gear.
No tune, no CAI and I'm running 245/70/17 Michelin MS2's (E rated)

City MPG is right at 13
Highway is 19.5 if I keep the RPM's under 1800
 

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I agree that 10-12 MPG on a 6000lb truck running 35's is not bad at all. I get approx 16mpg average running 33's. And alot have told me that their 4.8 gets worse MPG stock than the 5.3 due to it working so hard.
 

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I'd say you're doing well for having 35's.
When I bought my truck (used), I did NOT want AFM and the 4.8 was my only option for that. Had I known then that I could get a tuner and turn off AFM, I would have gone with the 5.3 for sure. I know a bunch of guys with the 5.3 that blow me away on MPG's (Most have AFM tuned to off)
 

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11lifted said:
So i had my truck for about two months now. I bought it as it currently is. Lifted with 35" tires. My MPGs have been pretty bad. On regular fuel i get a constant 10.6 mpg. On premium fuel i get about 11.6 to 12. I know it was going to be bad gas mileage for the way the truck sits but this bad? Or is this normal? I know that living in the NW probably does not help either with hills everywhere especially where i live. Whats a good way to improve it? I've been looking into getting a tuner soon. Truck already has a K&N air filter and no-name dual exhaust. Any help or suggestions is appreciated.
First off you need to find out if the truck has been re geared If not, for the 4.8 and 35s i would look at a 5.13 gear. then get a custom tune from blackbear, efi live .ect after those two mods you fuel mileage will be alot better and your truck will be happier.
 

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^^^^ I agree that the truck itself will be happier with a regear and tune. But i doubt the 4.8 with 35's would get more than 1-2 MPG improvement. I do know the transmission will last longer with regear and truck may pull harder with the tune. But with regear, programmer, and tune your probably looking at $1000 minimum. Thats assuming you dont need to change carriers and can do regear yourself. My regear to 4.56 from 3.08 was almost $1000 for parts alone. Thats why i am only running 33's and hoping i dont regret not regearing. That takes a long time to pay for itself with only a few MPG improvement. BUT, transmission will thank you for it.
 

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Definitely get an economy tune. I have 3" of lift on my 03 Sierra 5.3 running 33's. Right now, I've got a Bully Dog performance tune which has given me a 1-2 mpg increase and lots of power. I've been getting anywhere from 12-17 mpg with it. Also, I don't know what your driving habits are, but go easy.
 

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Discussion Starter · #10 ·
DarkGothic said:
Definitely get an economy tune. I have 3" of lift on my 03 Sierra 5.3 running 33's. Right now, I've got a Bully Dog performance tune which has given me a 1-2 mpg increase and lots of power. I've been getting anywhere from 12-17 mpg with it. Also, I don't know what your driving habits are, but go easy.
Would you recommend going with a bully dog? I have been debating between bully dog and intune. Lots of people on here are with intune but i still can't decide
 

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Diablosport Intune will allow custom tuning. Diablew is a sponsor here and will work with you on a custom tune. I still wouldn't expect any major increase in MPG. Best improvements come from driving style improvements. Drive like there's a raw egg under your gas pedal. Keep your RPM's under 2,000 when shifting. Slow down and coast to red lights and stop signs. Avoid hard accelerations. Make sure your tires have proper air pressure. all of these are free and will provide better results than any mod you can buy.
 

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I agree with TooTall, it's driving style more than anything once you get past the lift and the 35's. I only live 3.5 miles to the office and it's mostly side streets with 16 stop signs and 4 traffic lights. If I drive like a granny, I can coax 15-16 mpg out of BART. I did that for about 3 weeks, then decided that I prefer driving like a maniac than saving a couple of bucks.

:twisted: :twisted:
 

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Thought i would chime in, i'm 35's on 8" of lift with stock 3.42's and a tune now wiht Intake, exhuast and Servo's.

When i got the truck it had intake and exhaust already done and was getting 10.3 best....

I did the Tune - I see 12.7-13.5 city, and can put down 14.5 on the highway, all 87 octane...

I'm doing regear if I keep the truck and I expect 1-3 mpg honestly.

Tuner helped me alot - the bump from 10-13 was HUGE for me.
 

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Did you recalibrate the speedometer? May not be as bad as you think. I get about 16 on the highway under 60mph, raised 4", flowmasters, and 33's. As others have said, drive it right, I'd say keep the ac and power accessories off. Mine was also way out of alignment. Keep the oil and fluids clean. And keep in mind you are putting gas in a truck that's worth it.
 

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Do people really see an increase when going to a bigger gear ratio? All that does is trick the truck into thinking it has stock tires, when the RPM's were actually lower with the bigger tires (bigger tires spin the inside of the wheel slower). I definitely agree with it being better on the tranny, because right now the truck is like you walking with mud covered shoes. But with the right gear, the RPMs would be up. Higher RPMs means lower MPG. Wouldn't it be more like a tradeoff?

On the upside!! Your truck will feel much faster with the correct gears then any upgrade could make it.
 

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The higher rpms doesn't necessarily mean more fuel consumption.

Without the regear the motor is burning more fuel trying to get up to speed than it would if it's geared correctly. Also on my old truck with 3.73s and 33s it seemed to constantly want to downshift at 70-75 my on the highway. This all will affect gas mileage tremendously.

Sent from AutoGuide.com Free App
 

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draggo144 said:
Do people really see an increase when going to a bigger gear ratio?
Yes, because it brings back any mechanical advantage that was lost due to the increased tire diameter. Obviously, you can go too low and have poor mileage as well.
 

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I got my 08 GMC Sierra 1500 with 33's on it. I have a K&N cold air intake and a throttle body spacer. I also have a Edge CTS that i run in economy, and i get between 22-25 MPG. I have the 4.8 w/dual exhaust. Its not a 4wd drive but, with a 4wd it should still boost the MPG and even horsepower. An edge is definetly a good programmer to go with.
 

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Those are impressive MPG's with a 4.8.

Does anyone know if you speedo is not calibrated to your bigger tires with it scew your actual MPGs? I bought the truck with 33's and am almost certain the speedo was not calibrated. I drive the truck like a grandpa and get 12-14 consistently. Truck rarely sees 2k rpms. If the speedo hasn't been recalibrated would it show that I'm getting less MPG's because the truck thinks it's driving slower than it is?
 
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