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WTF, on Gas Mileage

This is a discussion on WTF, on Gas Mileage within the General Help forums, part of the LSx Technical Help Section category; Ok... 9,000 miles or so ago, I changed the plugs (irridium GM) plug wires, Seafomed the intake and a can ...

  1. #1
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    WTF, on Gas Mileage

    Ok...

    9,000 miles or so ago, I changed the plugs (irridium GM) plug wires, Seafomed the intake and a can in the tank cleaned the throttle body, Cleaned the MAF sensor correctly, cleaned the air filter, changed the diff lube, replaced the fuel filter. 7k ago, I replaced the O2 sensors.

    I run a bottle of Seafoam through the tank every 6 weeks or so. Tire pressures checked every week.

    I am getting 280-290 miles a tank on a 98 T/A. 80% of my driving is freeway, and I do not rag on her. T56

    I did have a flange leak, drivers side, corrected 4 days ago. I have noticed the temp gauge barely creeps past 170-175, and it takes a long time to get there.

    Is there anything else I should or could look at? Would taking it somewhere(first time in 10 years) and having a diagnostic be worthwhile?

    I know she is tired with 139k, but she still idles well.

    Am I being a bi-atch complaining about this, or is this mileage normal?
    Last edited by Banshee1967; 11-29-2008 at 08:17 AM.

  2. #2
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    I have talked to 4 people here in KY in the last week that have all seen a drop of 3 MPG.

    They are all over the state, so it isn't just a Louisville thing.

    Motorcycles, cars, trucks. My car is off more like 3.5 MPG.

  3. #3
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    79 T/A -91 Firebird
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    WTF. Im having the same issue. Always get at least 280 miles a tank. Getting like 180 now. Im really confused

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    Quote Originally Posted by JoshieDoom View Post
    WTF. Im having the same issue. Always get at least 280 miles a tank. Getting like 180 now. Im really confused
    Replace your O2 sensors... That was exactly my problem 8 months ago..No SES light at all..replaced both sensors up front by the motor and my mileage went from 180-200 to 300. Not as good as 330-340 that I used to get.

    I have a spare set of correct GM O2's if interested. They are the correct length and part #'s.

  5. #5
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    79 T/A -91 Firebird
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    Doubt its the 02s since i changed them recently.

    Mileage drop basically happened overnight just as driven has explained. Changed out my IAT sensor and that helped a bit.

    Where do you guys fill up?

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    I use BP to get the 5% off.

    People I talked to use everything from Kroger to Shell. I know my stepdad uses namebrand premium.

    I wonder if they have slipped in some blended crap on us.

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    Which O2's? Are not there 4 of them? The two in the front are the ones I replaced.

    Still 180 per tank was what I was getting..Replaced the fronts, and after a few days, went back to 300 per tank.

    I had checked EVERYTHING else other than the o2's because there was no SES light. A few guys here said there were 4, but I replaced the front two in half an hour as Orion and SunsetOrangeSS suggested.

    I have never filled up with anything other than BP 93.

  8. #8
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    79 T/A -91 Firebird
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    I only use bp premium. i have 1/16 tank of gas and i have to fill up in the next few minutes. Thinking of going to marathon.
    The rear two do nothing.. I dont have them.. no cats

  9. #9
    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Driven View Post
    I use BP to get the 5% off.

    People I talked to use everything from Kroger to Shell. I know my stepdad uses namebrand premium.

    I wonder if they have slipped in some blended crap on us.
    its time for them to be changing over to winter blend at the fuel stations....i wonder if that is what is happening to everyone fuel mileage

  10. #10
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    79 T/A -91 Firebird
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    Winter blend?

    Never had this issue since 05.

  11. #11
    cutting and welding mark21742's Avatar
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    Quote Originally Posted by JoshieDoom View Post
    Winter blend?

    Never had this issue since 05.
    winter blend is fomulated for colder weather and summer blend for warmer, they use different additives and ratios.
    i get my gas in maryland and pennsylvania and have seen a drop here in my mileage too.

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    I've never seen this happen before and I'm 27.

    Winter blend for diesel is the only chang eI know of. Gas would be a new thing.

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    I am on E now... Going to Shell and fill up. Will post results.

    I wouldn't doubt that alot of the premium still in the tanks is from the $4.39 a gallon days a few months ago.

  14. #14
    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Driven View Post
    I've never seen this happen before and I'm 27.

    Winter blend for diesel is the only chang eI know of. Gas would be a new thing.
    the diesel is less restricted in the colder months oey can use more anti jelling additives (like kerosene) to keep it from freezing in the lines.....yeah the man stuck it to us with gasoline blends too

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    I know all about diesel fuel.

    I've never heard of winter blend gas being used in KY.

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    Member 01 SS Vert's Avatar
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    You gas just change to ethanol blended recently?

    Our did this year (up to 10% Ethanol) and I noticed 30-40 miles less per tank. I now shop at NON ethanol blended gas stations if I can find them.

  17. #17
    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Driven View Post
    I know all about diesel fuel.

    I've never heard of winter blend gas being used in KY.
    blended fuel is spreading like a disease....

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    Quote Originally Posted by 01 SS Vert View Post
    You gas just change to ethanol blended recently?

    Our did this year (up to 10% Ethanol) and I noticed 30-40 miles less per tank. I now shop at NON ethanol blended gas stations if I can find them.
    How do you know if they were or weren't selling blended?

  19. #19
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    I see you're in michigan. Do you let the car idle a while to warm up? Keep in mind that your gas mileage is always going to suffer a little during the winter. The car takes longer to heat up and stays open loop longer so it uses a little more gas.

  20. #20
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    dude the most i ever got was 218 miles to the tank.....i wouldnt complain about 280.......i also never run the tank down past a quarter full

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