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  1. #1

    Default Poor MPG. New plugs, wires next?

    Hey all,

    My Avalanche has been averaging around 12 MPG per tank. It's 4x4 with 3.73s, stock ride height, with Diablo 87 octane tune, and a K&N CAI. I made sure I reset the computer by disconnecting the battery after I installed the CAI. Anyways, last weekend I decided to clean the MAF sensor and change out my plugs. These were the stock plugs with 70k miles on them. I replaced them with Denso Platinum TTs (PT16TT) because I figured I'd trying something different. Next might be wires if my mileage doesn't improve much. Any other ideas? Also, what do you think of the plugs below?


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    -2008 Chevrolet Avalanche LT 4x4 w/ K&N CAI
    -2012 Kia Soul !
    -2003 Kawasaki Ninja ZX-6R 636

  2. #2

    Default

    Are you throwing any codes?



    If at first you don't succeed, chances are, you are using too small of a cheater bar

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  3. #3

    Default

    Quote Originally Posted by rileyjr16 View Post
    Are you throwing any codes?
    No codes. I even check every once ina while.

    - - - Updated - - -

    Quote Originally Posted by rileyjr16 View Post
    Are you throwing any codes?
    what did you think of those plugs? Pretty dirty?
    -2008 Chevrolet Avalanche LT 4x4 w/ K&N CAI
    -2012 Kia Soul !
    -2003 Kawasaki Ninja ZX-6R 636

  4. #4

    Default

    Yeah. Mine looked like that after 40,000. But my knock sensors need to be replaced. You don't drive like a bat out of hell I'd assume. Does it have the 5.3 or 4.8?

  5. #5

    Default

    I don't think those plugs look that bad. Other than changing plugs, modern engines don't require much of a "tune up" like they used to. Change the plugs and fuel filter, clean the air filter and keep the tires aired up (go a little above the recommended air pressure on the door, maybe 5 to 10 pounds) and you should be getting most out of your fuel mileage.
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  6. #6

    Default

    Quote Originally Posted by rileyjr16 View Post
    Yeah. Mine looked like that after 40,000. But my knock sensors need to be replaced. You don't drive like a bat out of hell I'd assume. Does it have the 5.3 or 4.8?
    5.3L. I keep the rpms under 2000.
    -2008 Chevrolet Avalanche LT 4x4 w/ K&N CAI
    -2012 Kia Soul !
    -2003 Kawasaki Ninja ZX-6R 636

  7. #7

    Default

    The plug wires on the 5.3L V8 engines are really short, so they are really easy to replace. I don't know how much they cost, but it can't be that much.

    2013 Silverado LTZ White Diamond Crew Cab


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  8. #8

    Default

    That might be the next thing to do after I take it to the dealer. It's under warranty and I want them to see if there are any recalls or TSBs applicable to it and see if they can find anything wrong with the vehicle and fix it then.
    -2008 Chevrolet Avalanche LT 4x4 w/ K&N CAI
    -2012 Kia Soul !
    -2003 Kawasaki Ninja ZX-6R 636

  9. #9

    Default

    Fresh O2 sensors (front ones) might help. I like to change mine when the plugs are changed.

    But, the thing that impacts mileage is rolling resistance. Tire pressure, thread pattern, rubber compound, alignment. tight brake pads.

    Anything that increases the amount of power required to roll the vehicle will cut into the mpg.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  10. #10

    Default

    Quote Originally Posted by RayVoy View Post
    Fresh O2 sensors (front ones) might help. I like to change mine when the plugs are changed.

    But, the thing that impacts mileage is rolling resistance. Tire pressure, thread pattern, rubber compound, alignment. tight brake pads.

    Anything that increases the amount of power required to roll the vehicle will cut into the mpg.
    brand new Bridgestone Dueler H/L Alenza filled at 36 psi approx.

    I appreciate all of the responses. Maybe the truck is just THAT BAD on gas. My 2011 Silverado averaged 16 mpg and I thought that was terrible!
    -2008 Chevrolet Avalanche LT 4x4 w/ K&N CAI
    -2012 Kia Soul !
    -2003 Kawasaki Ninja ZX-6R 636

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