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Poor MPG. New plugs, wires next?

Discussion in 'Maintenance & Upkeep' started by cbroberts88, Aug 27, 2013.

  1. cbroberts88

    cbroberts88 New Member

    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?


    20130825_134805[1].jpg 20130825_134840[1].jpg 20130825_150400[1].jpg
  2. rileyjr16

    rileyjr16 Active Member 1000 Posts

    Are you throwing any codes?
  3. cbroberts88

    cbroberts88 New Member

    No codes. I even check every once ina while.

    - - - Updated - - -

    what did you think of those plugs? Pretty dirty?
  4. rileyjr16

    rileyjr16 Active Member 1000 Posts

    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. McClintoc

    McClintoc Super Moderator Staff Member Platinum Contributor 1000 Posts

    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.
  6. cbroberts88

    cbroberts88 New Member

    5.3L. I keep the rpms under 2000.
  7. stchman

    stchman New Member 1000 Posts

    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.
  8. cbroberts88

    cbroberts88 New Member

    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.
  9. RayVoy

    RayVoy Active Member 1000 Posts

    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.
  10. cbroberts88

    cbroberts88 New Member

    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!

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