how to improve fuel mileage on a 03

Discussion in 'Performance & Fuel' started by ChevyFarmKid, Feb 13, 2012.

  1. ChevyFarmKid

    ChevyFarmKid Rockstar

    I have a 03 silverado 1500 with a 5.3, 3.73 rear end, with 285/75/16 tires, mbrp dual exhaust. I'm only getting 12mpg, seems like i should be getting at least 15 or so looking at what others get. I have a new MAF sensor, new y-pipe w/ cat's, all o2 sensor's replaced, new fuel filter, I do all regular maintenance as well. if anyone has any suggestions, anything would be appreciated. Thomas
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    I would like to know what you have done for regular maint? plugs, filters? also you say 12mpg is that highway or city? and how are you driving doing that (ive had 3 of these trucks with the 5.3L and the milage on each was different)
    BTW that is a nice looking rig!
  3. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Have you adjusted for the taller tires?
    What came stock-maybe 265/70 16??
    They might be 2" taller than stock meaning you are actually getting maybe 1mpg better than calculated
  4. ajarman

    ajarman Epic Member 5+ Years ROTM Winner 1000 Posts


  5. Red Z71 Max

    Red Z71 Max Rockstar 4 Years ROTM Winner 1000 Posts

    Did you recalibrate the speedometer after increasing your tire size? This will throw off your speedometer , odometer and fuel mileage. Also a free breathing Cold Air Intake combined with a less restrictive exhaust can help. There is also the option to purchase a handheld programmer that has the ability to set the fuel management for fuel economy, towing, performance or stock. Diablo, Edge, Hypertech, super chips all make nice units.
  6. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Yes you definitely have to recalibrate for taller tires- or just do a little multiplication each time.
    For example if your OEM tires were 31" and current are 33"
    do this
    12MPG X33/31=12.7MPG
    Same story with what your odometer reads- multiply it by a correction factor
    You are going farther and faster that your odomter and speedometer are reading.
    Another thing-those wider taller heavier tires have more aero resistance and rolling resistance and take more power to accelerate(and brake) than the stock tires
    They have look to have fairly aggressive tread-probably more rolling resistance
    Oh-did I mention-Nice looking tires/truck
    Last edited: Feb 14, 2012
  7. ChevyFarmKid

    ChevyFarmKid Rockstar

    I bought the truck with 15,000 miles on it. When I bought it, it already had 285/75/16's on it from the dealer, so i'm not sure it's been recalculated or not. I have always run Schaeffer oil in it with WIX filter and changed it every 3k. I have also rebuilt the transmission and t-case. Looks like a programmer is the next step. Any suggestions for a Programmer?
  8. SuperSport01

    SuperSport01 New Member

    A programmer can help slightly and you can use it to correct for the larger tires. But a real dyno tune will be much more optimized and the dyno tuner can do many more things than a simple plug in tuner. Also cost really wouldnt be much different either way.
  9. ChromeSilver02

    ChromeSilver02 Epic Member 5+ Years 500 Posts

    Do you drive mostly city or highway? I have a 02 4.8L with 285/55/20 and I get 17 mpg and I drive a mix of city and highway. But I have always know that the way you drive will depend on the mileage you get. So easy on the accelerator will make a world of difference.
  10. SuperSport01

    SuperSport01 New Member

    I just had another thought. Since its an 03 it didnt come with electric fans like the 06+ trucks do. A set of electric fans will free up power and mileage.

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