Low mileage per tank

Discussion in 'Gen II Prius Fuel Economy' started by 2005PriusOwner2010, Mar 31, 2012.

  1. 2005PriusOwner2010

    2005PriusOwner2010 New Member

    Mar 31, 2012
    2005 Prius
    ----USA ONLY----
    I've owned my 2005 Gen II Prius for almost 2 years now. I normally average around 45 MPG on each tank of gas; however, the issue I'm having with my car is it seems that I'm unable to completely fill up the gas tank. The most I've ever put into my car was about 7.5 gallons, and that was with the gas light on and the last brick on my gauge blinking at me.

    I normally wait until there is 1 or 2 bricks left when I fill it with gas and I average around 300 to 325 miles per "tank". Whenever I fill up my car, I usually put between 6.5 and 7 gallons of gas into it. So, the mileage isn't really the issue, it's that my car supposedly has a gas tank that holds 11.9 gallons in it, but I've never been able to put anywhere near that amount of gas in it.

    I've done some reading on forums and found out that the amount you can put into a prius is determined by an internal fuel bladder, but I can't imagine that it would ALWAYS be this bad, especially over a 2 year period. Any other ideas as to what could be going on with my car?

    Thanks in advance!
  2. PaulHS

    PaulHS Member

    Feb 6, 2008
    SE PA
    2007 Prius
    Welcome to PriusChat!:welcome:

    The problem you describe is probably one of the most common complaints about the Prius. For the most part, you've answered your own question: it's the tank bladder. There is no single remedy but there are as many "solutions" as there are complainers. You might try additional reading here about the issue. Numerous threads discuss the subject.

    You don't say how you refuel. Pump Fast? Slow? Stop at the first click? Have you ever had the car belch gas out the filler tube? Most owners suggest pumping slow and stopping at the first click. (1)This does not work for everyone, although it's good advice, and (2)I suspect the results are as you've described: less than a complete fill.

    In PA, we hope for warm weather which makes the bladder more flexible, and enables a more complete fill. Even then, a 9 to 10 gallon fill is the best I ever see. That's not likely to be your problem though and speculating will not be helpful. Again, search through the forums for "bladder" and read the suggestions. One may work for you.
    1 person likes this.
  3. F8L

    F8L Protecting Habitat & AG Lands

    Aug 14, 2006
    Sacramento, CA.
    2013 Chevy Volt
    It is that bad. Most never get more than about 8 gallons in during a fill. My average fill was about 7-8ga for a 400 mile tank. 450-550 miles would equal about a 9ga fill but required me to drive on the flashing low fuel light for 30miles or more.

    One of the big pluses for the GenIII was the elimination of the bladder. I still only pump about 9-10ga during a refill but I know I cold go another 100miles or so on a full tank without stressing over the bladder issue in my old car.
    1 person likes this.
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers, Nadir of Wrongness

    Apr 14, 2009
    Greenwood MS USA
    2012 Prius v wagon
    I am in Mississippi but I find that my gas tank is much larger when it is over 80F.

    My 'voodoo' method: Open the gas cap before messing with pump, fill as fast as possible, when it clicks I am done.
    1 person likes this.
  5. RikM

    RikM Junior Member

    Jan 15, 2012
    2008 Prius
    It sounds like it's very much a case of ymmv :) .

    I've been filling my 2008 up on 2 or 3 pips. It takes 30 to 35 litres, in temps between 5 and 15 C.
    So, about 8-9 gallons at 40-60 F...
    1 person likes this.
  6. 2005PriusOwner2010

    2005PriusOwner2010 New Member

    Mar 31, 2012
    2005 Prius
    ----USA ONLY----
    I have always pumped the gas in slowly. If I put the pump on auto, it fills too quickly and it tends to auto-stop after a couple seconds. Because of this, I have always just held the lever on the pump about 1/2 between off and the first notch you can set it to. To answer your second question, I usually put in an extra dollar or two after I get that click from the pump. I appreciate the response!
  7. Rokeby

    Rokeby Member

    Jan 21, 2008
    Ballamer, Merlin
    2008 Prius
    It is possible that your gas tank inclinometers need to be reset.

    Here is information that was posted 4 years ago, almost to the day:

    Some information from the Toyota Tech Manual:

    "The direct acting fuel gauge is located in the sub tank. This gauge
    consists of a pipe surrounded by a coil. A float in the pipe moves up and
    down with changes in the fuel level. A magnet is attached to the float.
    The up and down movement of the float causes a change in the
    magnetic field. The flow of current through the coil creates a potential
    difference and the resultant voltage is transmitted to the meter ECU.

    "There are two inclination sensors located in the meter ECU to detect
    vehicle longitudinal and latitudinal inclinations and to correct the fuel
    level calculation. Corrections are made by the signals from the
    inclination sensors and the ambient temperature sensor located in the
    fuel tank.

    "The inclinometer must be reset if the customer complains that they can
    only pump a few gallons of gas into their tank or that they run out of
    gas with three or four bars left on the fuel meter. The inclinometer
    must also be reset if the Prius is refilled on an excessive slope or if the
    fuel gauge becomes inaccurate.
    Please refer to the Prius Repair
    Manual for the inclinometer calibration procedure. " [Emphasis added]
    Automotive Training and Resource Site

    Here is info on the proceedure that was posted somewhile back:


    Senior Member

    Easter Egg Time.... Anybody wanna reset the fuel gauge inclination
    sensor? Make sure your fuel level is somewhere between 1/4 and 3/4, and
    temp should be about 70-90 F.

    Step 1: PARK ON A LEVEL SURFACE!!!! If you are on a slope you will reset
    the sensor to an incorrect level!!
    Step 2: Press the ODO/trip button to turn the odometer to trip A
    Step 3: Turn off the ignition and set the parking brake.
    Step 5: Press and hold the ODO/trip button and press the Power button
    Step 6: Release and press the ODO/trip button three times
    Release-Press-Release-Press-Release-Press and HOLD.

    The Odometer on the combo meter should now be showing the normal
    mileage, as you hold the ODO/trip button down, the reading should change.
    Something along the lines of 650D0 or similar. The actual figures don't really

    Step 7: Release and press the ODO/trip botton once more and HOLD it in.
    The figure will change again. This time, only ONE digit will change.
    650D0>65010 as an example.

    Don't be afraid to try it. Even if it doesn't work, you won't goof anything up.
    Try, try again. It sometimes takes a half dozen attempts before you get it
    work right the first couple of times you do it. This only needs to be done
    once in a while. I would recommend once every ten tanks or so. I usually
    only do it when a customer has a fuel gauge issue. [Emphasis added.]

    Takes a bit of practice but it resets the ECU to try to be more accurate in
    it's estimation of your actual fuel level.


    Nihil novi sub sole...
    Nothing new under the sun :p
  8. dstrauss

    dstrauss Gas-Guzzler Convert

    Feb 1, 2012
    Midland, TX
    2012 Prius v wagon
    Never thought joining the Prius community was cover for weak bladders...
  9. edthefox5

    edthefox5 Senior Member

    Jul 25, 2007
    Clearwater, Florida
    2007 Prius
    The gas bladder is held under a slight vacuum so the bladder is collapsed against the fuel removing any spaces that will hold vapor.
    No air space no vapor relaesed from gas.

    If you open up the gas cap and immediately insert pump and start pumping you are using the fuel to expand the bladder as it takes a few seconds for the bladder to equalize to the outside atmosphere and relax. Plus fighting against the residual vacuum.
    This immediate pumping action disturbs the vacuum controled auto shut off feature in the gas pump itself resulting in premature pump shut off and or inability to pump in the required volume to fill the tank without multiple shut off clicks on the pump. Also Multiple clicks or force filling usually result in the classic Prius gas belch.

    Soluton is very easy. Open the cap and let the gas tank vent for 2 minutes. Giving the tank a moment to equalize and relax.

    Open cap, go in store for a minute or 2. Come out and fill up on SLOW only and hang up pump on first click always and you will never ever have a problem again. And it also helps if you don't let the tank get too empty. I always fill up at 2 pips or one solid pip.
    Have not had one issue filling up since I started filling up like this 4 years ago.
  10. AZGeek

    AZGeek Semi-informed Member

    Feb 5, 2012
    2012 Prius
    I usually go 130 - 150 or so miles past the start of the flashing bar and usually fill up with between 9.5 to 10.5 gallons. My most recent fill-up was after 618 miles on the tank, with the last bar beginning to flash at 442 miles. Fill up was 11.336 gallons to first click, 11.395 gallons after second shut-off. I usually go past the first shut-off, especially in warmer weather, because of the tendency for the fuel to foam and cause a premature shut-off. My technique is to slow down when I think I am getting close to full (haven't been able to get it right) and then slowly fill to second shut-off. I've done this for over eight years and have never had a problem with spillage or any adverse effects (stated so I can hopefully fend off attacks from those that are aghast over thoughts of over-filling a Prius and messin' with SULEV :lalala:).

    I think the behavior started after my very first fill-ups and realized the "sky is falling" flashing bar and reminder beeps were just plain baloney. I would much rather have an accurate gauge without some factory applied fudge factor.:rolleyes: