12.3 gal on fill up?

Just filled our "v" yesterday....2 bars showing..."43 miles to empty" on the display...9.71 gallons to fill....
The figures your brother provided remain a "mystery".....

 

^ It's not a mystery to me.
Some Gas-N-Go out there has a defective pump, or an owner or operator with defective morals.
Either that or the brother has a defective memory or eyesight.

I'm a bit of a skeptic on one's ability to pump 12.xx gallons of fuel into a Prius that they drove into the Gas-N-Go.

 

I second the "defective pump or defective morals" suggestion. There's a gas station in Dallas that I know I can always fill up ~.5 gallon more than I can at any other gas station. And surprisingly, my mileage always calculates out worse with gas from that station.

 

if you have 43 miles to go and you pumped 9.7 gallons, that means at zero it would take 10.5? then, are there not another 2 gallons of safety? of course, 2 bars on the gauge makes no sense.

 

On the Gen 2, hypermilers have stuffed upto 12.87 gal. into the tank by filling up to the top of the fill tube repeatedly. I have gotten 12.1 into the tank personally, and the tank bars meter is notoriously flakey.

 

I would definitely contact your state department of weights and measures or whatever ya'll have that regulates those gas pumps. It's not uncommon for gas station owners to try and rip people off especially if its in a rural setting.

 

I've done 12.1 gallons so the difference, 0.2 gallons, is about a quart. This seems a little too much. I lean towards the pump calibration hypothesis.

Your brother can replicate the problem by running the tank dry and carry a 1 gallon pony can to reach the station to refuel. However, if plans to do this experiment, he needs to monitor the energy flow arrows once it starts "flash" as that is the only reliable indication the gas is gone, when the arrows go away.

Bob Wilson

 

When I'm at 2 pips I can only manage 8.x

 

On the 2010 model year and above prius family, not the "C" model, the listed
gas tank capacity is 11.9 gallons.

When filling up on slow speed when the pump shuts off on auto you can still pump
in another 2 gallons of gas which will be up to the top of the filler neck where
you can see the standing fuel. (I know about the fuel vapor canister being
compromised) but this is "True" gas tank capacity.

So,11.9 + 2 = 13.9 gallons.

 

I don't know if it is the filler neck or the last inch of the tank and
the filler neck, but I do know it is 2 gallons more when
filled that way. I don't recommend it as the vapor canister
being filled with gas may be an issue....

 

The filler neck holds very little, but there is an expansion space in the tank that is not intended to be filled. That is typically a couple of gallons of air/vapor space. Sounds like some people are managing to fill some or most of that.

I frequently fill my tank to the top of the filler but don't get that extra capacity, probably because I fill it relatively quickly then stop when the gas is well up the filler tube. How much longer does it take to to get the extra two gallons into the tank?

BTW, in addition to possible charcoal canister damage from over filling, if you really fill all the tank's expansion space with ground temperature gasoline on a hot day, the gasoline can expand and run out of the tank. I haven't heard of that happening yet on a Prius so suspect the 2 gallons of extra fill still leaves some expansion space.

If you managed to get a total of 14 gallons in a Gen III tank by overfilling it with 60F ground temperature gasoline, then when that gasoline had heated to 110F from the car sitting in the sun all day, the fuel would have expanded by...

Coefficient of volumetric thermal expansion of gasoline = 0.0006/degF, so for a 50 degree increase in temperature it would expand (0.0006/degF) x 50 degF = 0.03 or 3%.

3% of 14 gallons is 0.42 gallons or a bit over 1.5 quarts.

 

Assuming that when the gas pump shuts off, you are at the rated quantity of gas (11.9) according to Toyota, is not correct. Who knows what criteria Toyota used to decide how much the tank holds. Becides I've seen over a gallon difference when the pump shuts off from one pump to another. Generally when the pump shuts off you have about 10.8 gallons in the tank, if you can then put 2 more gallons in before you see the gas at the top of the filler tube. A lot of people have run out of gas testing various theories about how much gas they have left. My formula, and I have never run out of gas (520+ fillups), is to put one gallon in after the pump stops, and then never go more than 10.5 gallons worth according to the MFD. I usually go 9.5 to 10 gallons, and the empty fuel icon blinks for about 50 miles. If your careful you will never spill gas out of the filler tube, and you won't compromize the air filter.

 

I know that this is an old post but I thought I'd chime in... I bought a used 2012 Prius V about a year and a half ago. I consistently put 12 gallons of gas in the tank and have gone as high as 12.5 gallons. My frustration is that Toyota claims an 11.9 gal capacity but the auto shut off for almost all gas pumps trips at between 9 and 9.5 gallons which means that, if I don't "top it off" I am losing in excess of 100 miles. To make matters worse, topping it off is a slow and tedious process that can double the time it takes to fill up.

 

be careful you don't contaminate your vapor carbon system, that can be expensive