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Unbelievably bad fuel economy

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    #1

    Unbelievably bad fuel economy

    Hello! I have a 1994 Mercury Grand Marquis, and it is in great condition. roughly 70k miles (odometer has stopped working), runs great, interior is good, things like that.

    But here is the problem. I'm not sure if the fuel gauge is accurate or not (I hope it is), but if it is, I have some SERIOUSLY bad fuel economy.

    Here is how I take it: I filled up to Full yesterday at a gas station right down the road from us. Went home, and left the car for the night. Started it up the next morning, still on a full tank (hurray, no leaks!). I drive it to school (5.9 miles away), and drive it back home. BY THE TIME I GET HOME today, the fuel gauge has already dropped a WHOLE notch. So here is how I calculate it

    7 "notches" on the gas gauge including E (Empty) and F (Full)
    - 1/7 is approx 15%
    - The total drive time today was 11.8 miles (approx.)
    - The car has a 20 gallon gas tank
    - 15% of 20 gallons is 3
    - 3 gallons of fuel were used in 11.8 miles
    - 3.9 MPG

    WHAT THE....HOW can I only be getting 3.9 MPG? Any insight here? Don't get me wrong, I am not a crazy driver that is always flooring the pedal! I am quite conservative of my driving and I hate wasting gasoline. But even if you were to FLOOR it ALL THE TIME your fuel economy would never be that low.
    Last edited by AmuletOfNight; 03-03-2014, 11:00 PM.
    Tags: None
    #2
    Assuming no gas smell when filling her up....gas tank crack/seal while you were driving?

    siphon the gas out of the tank to an approved receptacle to see if it is the gauge.....or go to the gas station and see how much gallons it takes to fill her back up ?
    Last edited by Grand1; 03-03-2014, 11:31 PM.



    1978 Grand Marquis 460 2door "Blue Bomber"

    1987 LTD Crown Vic Canadian Tow Package 351w aka the "MI Mountie"

    1989 Colony Park ....Marge still lives!

    1979 Marquis creamy goodness

    Comment

      #3
      no gauge is that accurate. Only ever figure mileage off full tank refills and miles driven on that tank or averages of multiple tanks in similar driving.

      Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
      rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
      Originally posted by gadget73
      ... and it should all work like magic and unicorns and stuff.
      Originally posted by dmccaig
      Overhead, some poor bastards are flying in airplanes.

      Comment

        #4
        the guages aren't at all linear. There is more fuel between 1/2 and full than there is from E to 1/2 usually. There is also often some amount of fuel below E, and sometimes above F. The only way to really figure anything out is to drive a while, fill it up, and crunch the numbers from your odometer and the gas pump. If the odo doesn't work, maybe use a GPS to log miles.
        86 Lincoln Town Car (Galactica).
        5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

        91 Lincoln Mark VII LSC grandpa spec white and cranberry

        1984 Lincoln Continental TurboDiesel - rolls coal

        Originally posted by phayzer5
        I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

        Comment

          #5
          Have your fuel regulator check. It may be stuck.

          Comment

            #6
            Next time fill it up, drive to school and back to the gas station, fill it up again. This will tell you how much gas you used to school and back.
            89 Colony Park
            90 Colony Park
            70 HEMI Daytona Convertible

            Comment

              #7
              Can't calculate mileage in that small an amount driven. Fill your tank, drive about 100 miles, go back and fill it up. Miles driven/gallons to fill. This is the most accurate way.
              2020 Volvo XC90 T6 Momentum (Ice White / Blonde)
              2022 Ram 1500 4x4 5.7 Etorque, Built to Serve Edition, (Granite Crystal / Black)
              Past Panthers
              1989 Grand Marquis LS (Cabernet/Grey), 1989 Lincoln Town Car SS (White/Blue), 2004 Mercury Grand Marquis Ultimate (White/Black)

              Originally posted by Lincolnmania
              if its got tits or tires it's bound to give you trouble

              Comment

                #8
                Or do a resistance check on the sending unit.
                If it's misfiring, shaking, making smoke, it's probably getting that bad of mileage then.
                Also, like Gadget said, there more fuel available between full and 1/2 tank. The tank is tapered towards the bottom to ensure the pump has an adequate fuel supply even when the tank is low on gas. That's why the last part of the guage (from 1/4 to empty) goes go quickly.
                Your problem is likely caused by "there is no probem".


                -ryan s.
                08 Lincoln Navigator L - 233k
                03 Mercury Marauder- 63k
                97 Ford Crown Victoria HPP "Tank of Justice III" (TOJ3) - 194k -->578.9 miles on ONE tank of gas<--
                94 BMW 325i Convertible - 135k
                73 VW Super Beetle "Bunky" <----- Wifey's
                12 Mini Cooper S - 90k <---- Wifey's
                Originally posted by pantera77
                Well my buddy tells him he knows exactly who loves buying shitboxes.

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