Erratic gas gage on 2007 toyota prius

has anyone else experienced an erratic gas gage on their toyota prius? mine sometimes shows full when i’ve used at least 4 gallons of gas. i ran out of gas because i thought i had at least 3 gallons of gas when i had just about 1 gallon. aside from the embarrassment of running out of gas in a prius - a brake light lit up later and i was charged $94.00 to “reprogram the computer.” i am very angry because of the charge and because the toyota public relations department won’t refund my money.

I think that part of the problem is that you are assuming that a gasoline gauge is a laboratory-grade measuring device when it is actually just a device that gives an approximation of how much gas is in your tank. Many gas gauges will show “full” until as much as 1/3 of a tank has been used, so I don’t see where yours is very different.

If I thought that I had only 3 gallons of gas, I would immediately begin looking for a gas station since I know that this estimate is only that–an estimate. If you don’t want to get stranded, I think that you should do likewise.

The one thing that I don’t understand is the need to reprogram the computer. Please elaborate on what led to this need. Unless you abused the vehicle, it seems to me that this is something that should be covered under the warranty. When my Subaru was about a year old, the dealer updated the computer program in order to provide faster ignition when starting the car, and this service was free.

Why did Toyota charge you for this? The circumstances must have had something to do with this fee, but you did not share the circumstances with us.

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?

In brief, the Prius has a variable-capacity fuel tank containing a flexible bladder. Although the manual for my 2009 Prius says the fuel tank capacity is 11.9 gallons, the service department says it may be less than that at times. Apparently it depends at least partly on the outdoor temperature. I recently ran out of gas, and when I refueled only 10.5 gallons went it. The only warning that I had run out of gas was that four lights came on: the master warning light, the malfunction indicator lamp, the brake system warning light, and the VSC (vehicle stability control) warning light. If you run out of gas in a Prius, you may or may not be able to drive it on just the battery. I was lucky - I was able to continue to drive, and I was very close to a gas station at the time.

I’ve heard that the gas gauge can be very inaccurate, but I have not had that trouble with mine. In fact, at the time I ran out of gas, it had been flashing the low fuel warning for some time. The reason I kept going was that I had done the math, using miles driven since last fillup, average MPG since last fillup, and the stated capacity of 11.9 gallons. (Also, every other car I’ve owned has had a gas gauge that indicated empty way early.)

A forum on the topic of Prius fuel tanks and gas gauges is at