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  1. #1

    Default Why the decrease in my MPG?

    about a year ago i purchased a 06 Silverado 1500 5.3L v8. The vehicle advertises up to 20mpg in the hwy. I wasn't expecting to get the 20 in the hwy so I was ok when i was getting the 17mpg on the hwy. However, in the past couple months i have been getting a consistance 14mpg on the hwy and in town. Can anybody give me some advise on how to fix that?

    I like in a rural area where gas is $4 and up and have to drive a minimum of 250/wk and make a 900mile round trip across texas about 4 times a year. i would really like to get my milage up. I appreciate any input.

  2. #2


    How many miles on truck? What maintance have you done? Have you cleaned the throttlebody and MAF sensor since you've owned it. We need this type of info to help you. Also welcome to the club.

  3. #3


    X2 what Silveradotrailblazer said. Also look at your air cleaner and tire pressure. A few of seemingly small things can add up to a problem. And welcome to the club.

  4. #4


    Thanks for the welcomes.

    All I've really done is changed the oil and check fluids. Aside from that I'm pretty useless when it comes to vehicles.

    The truck has 76,000 miles. I've done about 20,000 of those.

    Is it easy to check those thinks on your own or should i take it to a mechanic?
    Last edited by onejon; 04-18-2011 at 06:10 PM.

  5. #5


    Well the spark plugs are good for 100,000 miles so your good there. As goldie says, the air filter and tire pressure. I would clean the throttlebody with throttlebody cleaner, not carb cleaner and use a soft toothbrush. Also clean the MAF with some CRC MAF cleaner. Its in a silver can. Clean per cans instructions. Use ONLY MAF cleaner to clean the MAF, otherwise you WILL ruin it.

  6. #6


    Dont know if your already running synthetics in the engine, trans, and rear axle, if you arent next lube change might be a good time to make the switch.
    Take a good look at how much stuff your carrying in the truck also, extra tool box's and spare parts add weight that cut into your mileage, if you dont need them leave tham at home in the garage.
    How many add on parts have you put on the truck to make her look pretty? Big front bumpers (your from Texas thats almost a requirement) bug shields, window vents, all theses items "dirty" up the trucks profile and make her burn more fuel to get around.
    As was posted first check the aircleaner and tire pressure then look at averything else.

  7. #7


    I changed the air filter already. I haven't added a bunch of stuff to it (like a bumper lol) the tires are just 31in.

    I use mobil 1 oil

  8. #8


    I run Mobil 1 in the entire truck, engine, trans and f&r axles. As I mentioned before clean the throttlebody and the MAF.

  9. #9


    What are you running for tires? Are they new recently?
    When you hear hoofbeats, look for horses not zebras.

  10. #10
    Sr. Mechanic LSU truckman's Avatar
    Join Date
    Jan 2011
    SouthWest Louisiana


    I've been getting the same poor milage out of my 2000 Silverado with the 5.3 and my wifes 2003 Lincoln with a 4.6 in the past 6 months or so. Both started about the same time. My 2011 GMC 5.3 4x4 is getting better milage than both my others. I have been told that all the gas stations have started using the 10% ethanol blend. I'm thinking this may be why the milage is dropping on the vehicles that weren't calibrated for that type of fuel and it's not effecting the newer E85 vehicles as bad.
    Just a thought. My older vehicles stay tuned up and maintenance is never neglected so that's about all I can think of.

    Current Motorvation:
    2011 GMC 1500 4x4 crew / 5.3, 6spd, 342 rears, g80 locker, bone stock
    2000 Chevy Silverado Excab / 5.3, 373 rears, g80 locker, 93 oct perf. tune
    2011 GMC Acadia Denali wifes ride

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