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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?



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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?

  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!
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  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.

  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.

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  8. #8

    Default

    Quote Originally Posted by RayVoy View Post
    My '09 is not as bad as yours (it does have the 6 speed tranny and 3.42 gears). A lot of city and a bit of highway will give me around 16 mpg (at least, that's what the DIC tells me).

    As I posted in an other thread a couple of days ago, I tried a speed test last week while driving in ME. 45 mph gave me the best mpg (around 25), 55 to 60 knocked it down a bit (I think it was around 20 mpg), driving at 75 knocked it down to 18. Speed makes a difference.

    I change the front O2 sensors when I change the plugs, because I've read that they start getting lazy around 80k, if this is true, or not, IDK.
    Thanks for the info! I would love to get mileage like that!

    - - - Updated - - -

    Took the truck to the dealer today. They said they checked everything and it all seemed fine. maybe the truck is just that bad on gas. oh well. I went ahead and changed the plug wires as well.

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