I think the gas gauge is a well-known flaw with Prii. I filled up and drove nearly 200 miles with the gauge reading FULL the whole time. Then watch it plummet from FULL to 3/8 in about 100 miles.
I’ve heard that it has something to do with the rubber bladder in the tank being more/less pliable with temperature changes. I don’t know.
I never rely on it. I keep an eye on average fuel consumption and miles driven since last fill-up. If you always fill it up (or know how many gallons you added) you will have a better idea as the Prius resets its milage report whenever you add fuel.
As for the assertion that 3 gallons necessitates a stop at the next gas station, the Prius only has an 11.9 gallon tank, so that should be a 1/4 full tank or enough to drive 150 miles at my average mileage. I wouldn’t head out on a long trip with that, but around town I wouldn’t panic.
I too would like to know why Toyota thought that you should pay the $94? Did they try and blame it on running out of gas?