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Thread: poor fuel economy

  1. #1
    Join Date
    Jan 2010
    Location
    spanaway wa
    Posts
    419

    poor fuel economy

    hello everyone,
    my fathers 2003 yukon has 110,000 miles and for some reason it is only getting 15 mpg on the highway, it has a coldair intake and all maintance is up to date, it use to get 20 mpg. the only thing that has me worried is the trans, it shifts hard and makes some noise, could this be the root of the bad mpg? thank you very much.

  2. #2
    Join Date
    Jan 2009
    Location
    Round Rock, Texas
    Posts
    1,699
    Changed the fuel filter lately?
    cjriojas:if you're weather man is a 5 gallon bucket, YOUUUUUUUUUUU might be a redneck
    danger_ranger83: I see now why it cost so much to get a harness made... FML
    2boostedSilverado: I like Casey's rear end, I want to chat with him about it

  3. #3
    Join Date
    Aug 2007
    Location
    Honeywood, Ontario
    Posts
    6,994
    Plugged up cats maybe?
    2006 Silverado
    Little Black Bitch

  4. #4
    Join Date
    May 2009
    Location
    Plainfield, IL
    Posts
    2,036
    what's the weather like? Both my trucks lose 3-4 mpg when it's cold out...and I generally don't let them 'warm up'. Idle for 1-2 minutes for the oil to heat up, but that's about it.
    blown transmissions are about as useful as 97% of the guys on this forum

  5. #5
    Join Date
    Jul 2009
    Posts
    168
    15 mpg? That sounds great. I haven't got that in three years.
    2002 Under Construction Again!

  6. #6
    Join Date
    Jan 2010
    Location
    spanaway wa
    Posts
    419
    no it hasnt had the fuel filter replaced i will do that next weekend. Is there a way to check for plugged cats? the weather is mid 40s and low 50s, the yukon has always gotten 18-20 mpg no matter the season. And i keep telling my father to let it warm up , but he just fires it up and drives. any more ideas would be most appreciated. thanks again.

  7. #7
    Join Date
    Jun 2010
    Location
    West Texas
    Posts
    406
    O2 sensors with alot of mileage get lazy and will give poor MPG's. But only the upstream sensors.
    RUN WAT U BRUNG!!!!

  8. #8
    Join Date
    Nov 2003
    Location
    Denton Texas
    Posts
    20,540
    improperly inflated tires will decrease fuel mileage, too. If he's hauling more passengers or cargo than normal or heavier passengers it will cause a loss of mileage, too. Check the wear pattern on the tires, too. Alignment issues will rob MPG.
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  9. #9
    Join Date
    Jan 2010
    Location
    spanaway wa
    Posts
    419
    i went through the whole suv and everything looked fine, clean air filter, brand new tires inflated to the right pressure. the one thing i havent done is replace the fuel filter, how hard is that to do? thanks for all the help and advice.

  10. #10
    not very hard at all. IIRC, the filter has quick disconnects at both ends. it sits at about the left rear door, just infront of the tank. another thing that can also cause poor mpgs is old plugs and wires. i need to do the fuel filter, plugs and wires on my 01, along with replacing my rims. but the rims will get changed next week

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