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  1. #1

    Default 10 MPG highway in a 2012 Denali???

    My friend and I picked up her 2012 Sierra Denali 1500 on Monday. She called me yesterday complaining that her truck felt like it was skipping and said she was only averaging 10mpg on the highway... That can't be normal. Any suggestions?
    00 Chevy Tahoe LT, 5.3 4x4

  2. #2



    I would suggest taking her truck back to her dealer to have this issue diagnosed.

    Evan, Chevrolet Customer Service

  3. #3


    I'm bringing it in tomorrow morning.

  4. #4



    Let me know how everything goes at the dealership.

    Evan, Chevrolet Customer Service

  5. #5


    ya somthing deff sounds fishy with it good luck hope they can get it all worked out
    2004 gmc sierra ext z71 5.3
    KB racing hot pipes 3.5" : 76mm turbo: 4l80e : Circle-d 2b multi disk :Walbro 400 : Racetronix Hotwire kit : TB coolant bypass : Nelson 91 Pcm : Tr 220 Cam : Brian Tooley double springs kit : Ls7 Lifters : Stage 3 heads : Custom Intake Manifold :80lb Injectors : Ported TB : 40k tranny cooler: Plx dm-100 gauge: Auto meter fuel and boost gauge:
    Custom Speedo : Leveling kit :Smoked led taillights and 3rd break light : Black projectors and fogs with hids : Blacked out grille : 33's on 16's : Clarion flip screen: sound que 12" subs: clerion 6x9's : Memhpis amps: Alpine componet set.
    Future mods... Detriot tru-trac, deviels own stage 2 meth kit, MORE BOOST!!!!!!!!!!!!!!

  6. #6


    So, I picked it up tonight, and brought it home to bring it to the dealership for her bright and early tomorrow morning. So, I was messing with things and was reading somethings and am wondering, do you have to manually reset the AVG FUEL ECONOMY Gauge? It stayed pretty consistent switching from back roads, heavier traffic roads and the highway..> I got in the truck it was 10.7, By the time I got home, it climbed .1 at a time, about every 10 minutes, until I got home and it was at 11.0. So I'm wondering if this just is an average mileage based on what the truck has consumed since being fuel up at first?.

    Are these trucks available with the Fuel Management systems? I'm guess that's what she was talking about when it "Cuts out" because I noticed at cruising speeds, the RMPs would drop even though i was still in on the gas... I just wasn't sure if these trucks came with that or not since I'm not well versed on the newer models...

    Another thing I noticed was that it kinda lags when first taking off from a start... Would that have to do with the electronic throttle control? It just seems like a delayed response... Actually, it seems like a lot of things are delayed. The back up camera when putting in reverse, the side view mirrors when putting in reverse.... There were two other things I noticed but can't remember now... Blahhh

  7. #7


    The feeling of delay when taking off is most likely the torque management. The AVG FUEL ECONOMY is for all time, if it's never been reset. Fill the truck to half tank, reset the AVG FUEL ECONOMY (hold the button in until it clears to 0), and see what it's at when you get down to 1/4 tank. In mostly city driving it should be around 12-13 average. If you were seeing 10 I guess it's not that bad, and may be from mostly test drives with people stomping on the gas pedal or such. Also, a full tank of gas is a lot of weight, and reading the AVG FUEL ECONOMY on the dash might seem lower than normal, particularly in city driving, as it will be lower until you burn about a half tank of gas, then it should start going up to stay around what the EPA estimate is for the rest of the tank.

    If the truck is used for mostly city driving, and it isn't driven very far each day, it might be best to only ever fill it up to 1/2 tank at most. You'll get slightly better city MPG due to the lower weight of having only 1/2 tank of fuel in it.

  8. #8

    Enkeiavalanche's Avatar
    Join Date
    Apr 2010
    Piermont,NY, back in Northern NJ now, But may be in IL soon....


    It's a new truck I only reset mine 1 time and with 83K on it I avg 14.6- 14.8 Thats city and Highway and a Heavy foot at times.. This is your true AVG MPG..
    08 Z71 Avalanche Mods to date: K&N CAI,Hellwig Swaybars and End Links, Corsa Sport Exhaust, Superchips Programer,IPCW LOF & 3rd brake light and tails, AMI Gas door,Show Hooks and Door locks, Enkei Wheels, with Pirelli tires, StreetScene Bowties, Grant Steering wheel,Muth signal mirrors,SSBC Big Brake kit,Huskyliner Mug gards,Floor mats and Hood shield, McGard Lug nuts and locks, Bedrug, Cervini's Ram Air hood,35watt HID Fog lights, Sylvania bulbs all around ZXE's Highs and Lows, WhiteNight Back up lights,Sirius and HD Radio, SnugTop sitting on deck now Got a Softopper on now,Tempress Boat Hatches.... New Bilstein shocks are on... New Mods coming soon..... X

  9. #9


    Yeah, I went poking around last night and figure out how to reset the gauges... as for the "cut out" the dealer said there was nothing wrong with it... I still think otherwise, but its not my truck, so i'm not gonna push the issue with it.

  10. #10


    I'm not sure what you mean exactly by 'cut out' here. If the RPMs are dropping on the highway without letting your foot up (assuming you aren't pushing it down further), it probably shifted into a higher gear. Are you driving with the transmission in "M" mode?

    As for fuel management systems, all the GM vehicles have had some sort of electronic controls on them since the 80s. All the current new vehicles now have torque management and electronic throttle bodies though, so the gas pedal is not a direct connection to the throttle body, but the throttle opening is conrolled by the ECM, based on several factors, only one of which is how hard you're pressing the gas pedal.

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