Low mileage per tank

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.

 

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.

 

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.

 

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...

 

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:

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"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]
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Automotive Training and Resource Site

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

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Bear68
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 4: DO NOT STEP ON THE BRAKE PEDAL! AT ALL! IT ISN"T NEEDED FOR
THIS PROCEDURE!!
Step 5: Press and hold the ODO/trip button and press the Power button
twice.
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
matter.

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.

GOOD LUCK!!

Nihil novi sub sole...
Nothing new under the sun

 

Never thought joining the Prius community was cover for weak bladders...

 

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.

 

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.