Gas gauge recalibration?

No calibration issues. People have been known to get around 50 miles after it starts flashing. I have seen very similar fill ups when I pushed it. They "error" on the side of safe. Also you will learn in time that the "computer" generated" mpg reads +3 mpg on the happy side. Example: If the computer says 50 it's more like 47 mpg. At 11.9 gallons you were getting very close to finding out why you DO NOT want to run out of gas in a Prius.

The Gen II guys had problems though with the bladder tanks.

 

When DTE stops at 0, you have about 1.6 gallons left in the tank, states the many threads posted on here already.

 

You're looking for a solution to a problem that doesn't exist. The gas gauge is cautious, trying to prevent you have a perilous highway walk with a gas can. Fill up when it's moderately low, stop pumping when the nozzle kicks off, done. Trying to squeeze more gas in can lead to spillage, mess up the vapour control system.

 

The Prius has a generous fuel reserve for obvious reasons: Running out of fuel in the Prius can be very problematic. Call it insurance. In my 5+ years of ownership, I have never had to put any more than 9.6 gallons in the tank. On several occasions I’ve had to ( according to the fuel gauge) run the car to below “zero miles remaining.”. Brinkmanship? Maybe, but understanding my car’s little quirks makes it a safe bet.

 

Same experience here. I have never been able to put in more than 9.8 gallons of fuel even after the low fuel light has been blinking. I too would prefer the gauge to be accurate not conservative.

 

This sounds about right. Only your expectations are out of calibration.

It should take 11.9 gallons only if you actually ran out of fuel. Bob Wilson has done that many times as part of his engineering curiosity. For this particular issue, he ran more than 100 miles farther than you went. For details, read just the first post of this too-long thread:
[WARNING] Running out of gas (Gen III) | PriusChat

 

Is this a new phenomena or did you recently purchase

 

Other than for an experiment, why would anyone WANT to run out of fuel????
I found it's best, at least for me, to fill up between 1/2 and 1/4 empty tank.
But you're playing with fire if you wait till the last marker is flashing....

 

People don’t like stopping for gas.
That’s why they invented plug ins.
Full tank every morning

 

I can calculate that each PIP on the fuel indicator equates to one gallon of fuel. In turn , this calculates to about 50 mile per PIP. In terms of file gauge accuracy, it probably doesn’t get any more accurate than that. You just have to remember that the guage only reads 10 gallons. After that, your are into an emergency reserve of about 1.5 gallons. All this is based upon a rule of thumb average of 50 MPG.

 

First, I echo Mendel Leisk's advice that trying to squeeze more gas in can mess up the vapour control system.

Second, people seem to get upset that others are running close to empty and think its "stupid" not to fill up when there's still a substantial amount of gas left. I don't know why people feel that way. Stopping for gas takes time, especially on long trips when you have to get off the freeway. I think it is reasonable to ask what is the reasonable "no risk" assessment of what the gauge is telling you.

Anyway, this thread is a good summary of how much gas is left:

.

Third, no one has addressed the actual issue you raise in your post:

What jumps out at me is that you have detected a change in the behavior of the gauge. That it took more gas to fill up two or three months ago and now it takes less when the gauge is still indicating the same is the interesting question in your post. Unfortunately, I don't have an answer for you, but maybe someone could explain this change in behavior.

 

agreed, that's why i asked the question in post #8

 

Yeah guilty as charged.

 

Some fella here who I won't say his name, but he put a gen 4 engine into a turd gen and drives 125 miles after DTE is at 0.

 

There's no emergency reserve.

 

Ok. Pucker factor Reserve; 1.5 gallons; after the fuel gauge indicates zero mile left.