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Discussion Starter · #1 ·
So, I'm trying to just understand why I'm gettin such shitty mileage. Truck is a 2011 CC 5.7 4wd with 3.55s. All that I've done to it is a 2.5" leveling kit, 275/65R20 Toyos, KN drop in and a Flowmaster 40 muffler in place of the stocker. I get anywhere between 10.5 and 11.6 depending on how nice I am to it. Just seems terribly low to me.

Thoughts on how I might improve it?
 

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That is terrible, I get better than that on a daily basis....

Not much you can do for an '11 besides cai aand exhaust. I just ordered a Vararam and Fastman TB. Hopefully it'll compliment my Magnaflow.
 

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Discussion Starter · #4 ·
I've done both manually and by the readout. Thats the 10.5 to 11.6.

I dont get it. I got around 15+ stock, and then just bam, off the cliff. I dont know if a switch to a magnaflow would help much. Need to check the filter I guess. I'm just thinking, if I lift it on 37s, I'll be getting 8...which would suck. I'll still do it, but itll suck.

Granted this is all 100% "city" mileage. I live about 3.5 miles from my work, so I never really get to wind it out much.
 

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Somethin dont seem right at all. Take it to the dealer for some flashes! God knows I've had at least 10 lol.

When I was in Arkansas last week, for example I got 11.3 mpg. That tank was used for city drivin in Blytheville, 3 days duck huntin with 4wd used most of the time and 2 nights nites out muddin.....
 

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sucking milage

It is a shame that the truck is advertised as getting 20 mpg. I also am deeply dissapointed in my 04.5 dually diesel. Just spent $3000 on reman injectors, Air Dog II, and a juice w/attitude and a CTS and only get 14.5, It got that before all the money waisted. I feel your pain. Anyone with answers?..
 

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i got nothing for you but.. try ballet snoes insted of your size 15 lead lined boots!!! Wow something dosent seem right at all....
 

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Discussion Starter · #8 ·
Ill admit I am pretty heavy on the pedal, but still, I drove the same when it was bone stock and I was getting north of 15 regularly. Nothing has changed other than my mods, and I almost always fill up with the same Shell gas, so that shouldnt make any difference.
 

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to the OP. Did you have 17" rims and swapped to 20" rims? If so, I would say it might be your speedometer is off. There is a 1" difference between the outer diameter of the 2 factory tire sizes (17 vs 20 rims). If you got even larger than stock then this will throw it off even more. This will throw your speedometer off and therefore affect your mileage calculations.

Here is the math:
Your current: 275/65R20 Outer Diameter: 34"

Stock 20": P275/60R20 Outer Diameter: 33"
Stock 17": P265/70R17 Outer Diameter: 31.6"

Assuming your speedo is off by 7.6% due to the increased tire size then
your 11.5mpg reading is closer to 12.3mpg (corrected). If my math is wrong someone please correct me.

I would say increasing tire size by 2.5" would increase the weight of the tires to the point where they would affect mpg as well (using 3.55 gears). Add that to the fact your leveling kit makes the truck less aerodynamic I would say you're close to where you where you should be.

FYI, if this is the case (and my math is right) then when your speedometer reads 60mph you are going 64.5mph

and I'll just throw this out there since it happened to me. The first sign of my torque converter going bad was my mpg dropped by 1-3mpg. I just had it replaced this week but first trip to work shows mpg back up to when I first bought it.


just a thought
 

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Discussion Starter · #10 ·
Nope, stock 20s the whole time, just the tire change. Not much of a change though, 275/60 to 275/65
 

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its the tires, speedo may be off some but if you have aggressive tread thats friction on the road. also if they r 6 or 10 ply they are heavier which is more rolling resistance
 

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I agree with HEMILANCER, most likely the tires took you south.
If that tread is any way shape or form at being more agressive, good bye mpg`s
 

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Not buying it" hemilancer" lil lift and slightly more agressive tire = -5mpg. You may be right but... i just dont see it. 2.5 level going in mine and i am going to see big mpg losses?
 

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Makes sense to me,

larger diameter tires(W/3.55s), more aggresive tread and heavier = 1-2mpg
level kit = 1-2mpg
speedo off= 1-2mpg
K&N drop in isnt gonna do much (it didnt for me), the upside to those are they last for ever.
Flowmasters are better than stock but are still restrictive ,
I would say you are right on the money with the mods you have equaling the mpg lose you are experiancing.
 

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Though I'm not going to modify my Dodge's lift or go to any more aggressive tires, I did do it on a full-size GMC Jimmy 4X4. I only did a 3" lift and went to some BFG All Terrain KO's that were only slightly taller. That truck used to get 17mpg under good driving conditions with a 350 engine. I was barely able to achieve 14mpg under the same conditions. Small lifts and even only slightly taller tires with more aggressive can make a big impact as some have already stated. And most times the slightly taller tires are also slightly wider.
 

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Granted this is all 100% "city" mileage. I live about 3.5 miles from my work, so I never really get to wind it out much.
Ill admit I am pretty heavy on the pedal.


Given these conditions and the more aggressive tires I think your doing OK.


.
 

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2.5 level going in mine and i am going to see big mpg losses?
With just the leveling kit you wont notice a loss (I haven't) but put bigger more aggressive tires and you will loose mpg's. On a 2wd truck I lost 2-3 mpg's after adding mud tires.


.
 

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Discussion Starter · #18 ·
Im anxiously awaiting a programmer like most everyone else as i bet i can gain a mpg or two that route. I may try a less restrictive muffler but considering my future plans ill be happy to remain in double digits.
 

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At the risk of being kicked off the forum let me make this observation; you buy a rig that has been years in research and development, designed by engineers who try to squeeze every bit of performance, driveability, power, comfort, fuel mileage and good looks possible out of the design. Then you start changing major components with off the shelf parts and expect things not to change? Just sayin'.
 

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Not buying it" hemilancer" lil lift and slightly more agressive tire = -5mpg. You may be right but... i just dont see it. 2.5 level going in mine and i am going to see big mpg losses?
i wouldnt say a 10 ply open country mt is a slightly more aggressive tire. its a mud tire not designed for highway driving.
 
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