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  1. #1

    Default 5.3L with active fuel management ~ Getting Terrible Fuel Mileage

    I recently traded back in june for a 2009 silverado z71 with the 5.3l and active fuel management. I love the truck, but it is getting terrible fuel mileage. I have been averaging 13 in town and like 15 if i am lucky on the highway. My last truck with the 4.8l averaged atleast 18 on the highway without AFM. So here is my question, how do i even know if it is working, anyone know? I dont have the model that has the DIC(driver information center) that shows current mpg and such.....any ideas? I have considered putting exhaust on it so that i will atleast be able to hear it when it switches to 4 cyl mode. Just sucks when it stickers at 14 and 19, and says with reasonable driving habits can expect up to 23 mpg on the highway.
    Last edited by mxracer919; 09-14-2009 at 06:03 AM.

    2009 Silverado
    5.3L LT1 Z71
    Rhino Liner over the rails
    20" Pro Comp Xtreme Alloys
    275/55/20 Pirelli Scorpion ATR's
    2.25" Readylift leveling kit
    Gibson Dual Sport cat-back

    1979 Cj7

    2008 Silverado reg cab short bed
    4.8L LS 4x4

    2001 Silverado reg cab short bed
    4.3L 5speed 2wd

    1995 Silverado ext cab short bed
    5.7L Z71

  2. #2
    Legend s5belford's Avatar
    Join Date
    Apr 2009
    Kalamazoo Michigan


    I have an 09 with the 5.3 and AFM, I don't have the driver infor center either and the best gas mileage I've ever seen was about 19 on the highway with about 14-15 in the city. I have an exhaust on my truck and it is nice being about to tell when it drops down from 8 to 4 but at the same time it sounds like crap, my only suggestion is a tonneau cover and I don't regret putting on the exhaust if that help you at all? good luck!


    2009 Silverado LT1: All Star Edition
    5.3 Liter V8 4x4

    Locking Rear Differential
    3.73 Rear Axle
    Fog Lamps
    Factory Remote Start
    Locking Tailgate
    20" Wheels

    Rear Wheel House Liners
    Molded Mud Flaps
    Stainless Nurf Bars
    Driver Information Center
    20% Tinted Windows
    Low Profile Diamond Plate Tool Box
    GM Bed Liner
    Silver Birch Metallic Mirror Covers
    Silver Birch Metallic Vent Visors
    Flowmaster Super 40 (knock off)
    20" Wheels
    Bed Rail Protectors
    Extang Tonneau Cover

  3. #3


    So how bad does it sound? I would do a tonneu, but I ride motocross so I have a bike in the back of my truck atleast once or twice a week. What kind of exhaust did you do? I did a cherry bomb pro muffler dumped under the bed on my 4.8l about two weeks before i traded sounded good, and was cheap too! bought the muffler off of ebay for 50, and had it installed for 50.

  4. #4
    Legend s5belford's Avatar
    Join Date
    Apr 2009
    Kalamazoo Michigan


    it doesn't sound too bad, don't really notice it unless I'm on the highway and I'm the only one hearing it, and if anyone else in the truck they don't usally know enough to hear it. It sucked at first but now its kind of nice being able to tell when it drops down to the 4. As far as the tonneau goes they are super easy to just roll up for putting your bikes, quad, etc in there. My exhaust is the flowmaster 44 knock off, and I just got the muffler because I haven't any duals that I really like and like how the stock dumps out so when its running 8 it sounds real nice, I spend $125 at the local muffler man, overall I'm happy with it. let me know if you have any other questions

  5. #5


    Im glad to get 13-14 my old dodge got 10-11 when i was being nice to the pedal
    2009 chevy 1500 z71 4x4
    2.5 ccm level,2.5 inch rear blocks 305/60/18 coopers stt,Debadged,10 series flow w/dual exit in front or right rear tire, KN CAI, diablo InTune, 18% tint all the way around ,spec-d euro headlights with black housings,winjet smoke LED tail lights,putco LED third brake light smoked, fab fours front bumper with 10k warn winch, RK sports ram air hood
    1965 c10 swb, zz4 350 with the hot cam and fast burn heads and a 780 Holley on top, richmond super street 5 speed,restorod

  6. #6
    Legend 2ToNe04's Avatar
    Join Date
    Apr 2009
    Fresno California
    Blog Entries


    afm mostly comes on highway driving where speed is steady.

    i might be wrong.

    2004 4.8| Custom Paint| Tint| De-badged| Shaved Tailgate| Rollpan| Smoked Tails| Color Matched| Lowered 5/8| Suede Interior| Color Matched Interior| Indash & TVs| Mids-Lows & 2 12" CVRs| 500 & 1100 Interfires| Soundeadener| Outlaw CAI| Magnaflow|
    Future Mods: 6.0 LQ4/9| Bags|

  7. #7


    Quote Originally Posted by 2ToNe04 View Post
    afm mostly comes on highway driving where speed is steady.

    i might be wrong.
    Yeah i figured that. Does anyone that has the DIC have any tips for the speeds at which it works the best? 65? trying to milk a little more mileage out of it. Just did the first oil change yesterday and went with the 0-30 mobil 1 fuel economy, that usually gets a mile or two per gallon.

    So.......any tips would be nice on driving speeds from you other guys with afm and the dic so i know what speeds to shoot for when i am out on the highway, thanks!

  8. #8


    I just went a drove the tahoe it seemed to only switch when i didnt touhthe gas at all and at and speed then right when i touch the gas itswitched back.

  9. #9


    Then again i never went over 70

  10. #10


    Did anything else change if how you drove between the two trucks? hauling more or less? Driving further? Did you move to a new location and on different roads (hills vs. flat, etc)? Are you in heavier traffic than before?

    10 Chevy Traverse LT AWD
    02 Chevy Trailblazer LS (110K+ miles - loaded except for 4WD - WRECKED!)
    99 Chevy Cavalier LS (105K+ miles - commuter car)
    78 Chevy Suburban Silverado (454, 3/4 ton)
    62 GMC 3/4 ton Pickup (350 police interceptor)

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