Stupid Fuel Gauge!!!!

It is not unusual for the top of the tank to register slowly on a car. 100 miles and still on full is a bit of a stretch, but not unheard of. I had a VW that didn't budge off full at 100 miles. Fuel level indicators appear to be very non-linear. On a Miata, 1st half of tank is 200 miles, second half is 100 miles. That's just the way they calibrated the gage.

 

That's normal... The rubber bladder inside the gas tank reduces pollution when you fill the tank up, but it makes the fuel gauge inaccurate... On PriusChat we refer to is as a guess gauge...

Imagine putting a standard water level measuring system inside a water balloon and that's the problem.

On long highway drives the pattern I most commonly see in my car after getting a tank as full as possible is first 100-150miles all bars are lit up... Then after the first bar drops off the rest of them drop off real fast till you get to 4 bars where it will sit again for almost another 100 miles.

As for your fuel tank capacity... Sometimes an old bladder inside the fuel tank won't hold much if the car was driven infrequently in a colder more northern city. But drive 700 miles or so of consecutive highway miles in super hot weather and always time filling tank with hottest part of the day and you'll be able to stretch that bladder out so eventually you'll be near 10 gallons, especially if you drive as long as possible before refilling so you're sure the tank is as empty as possible.

 

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They stop making the rubber bladder after Gen2, or maybe they still had them in the first year or two of gen 3, but did away with this problematic air pollution limiting technology in favor of more traditional solutions.

 

Some Gen 2 Gas gauge weirdness

There is a bladder inside North American Prius, so the tank holds more in summer when it is flexible, and less in winter when it is rigid. So in summer it may take 120 miles for the first pip to disappear even though in winter it takes 40 miles.

In MS I occasionally got 10 gallons in, but that is rare even in a hot and humid environment, below freezing you might get 6 gallon in.

Because of this bladder, the number of miles before you run out after the last pip starts blinking is variable. (I had a low of 8 miles)
Do not let yourself get down to the last pip. If your inlaws are in the car, don't let it get to 2 pips.

If you actually run out of gas, you must add 3 gallons before the computers will let you start the car. If you try too often, it sets a code and you have to clear the code to start.

 

On my 05 prius I can go to 130 miles before it starts to go down

 

Nope, no Gen3s had a bladder. Not even my first Prius, a model year 2010, from about one month into the Gen3 series production for the North American market.

The rest-of-world markets didn't have a bladder even on Gen2s.

 

Mine doesn’t go down until I’m over 100 miles, unless I don’t fill it right. Had 336 miles since last filled yesterday and still had 3 pips.

 

The gas tank was new technology at the time. Toyota figured out it was not such a good idea and dropped it. Nobody’s perfect. You should now drop Pips quicker. I wouldn’t let it go lower than 2 pips without a gas can with 4 gallons in the car. The gage isn’t known to be super accurate on the bottom end either.

 

My "Southern California" Prius often goes over 100 miles without a pip coming off the gas gauge. It has actually gone over 170 miles and still showed full. That never bothered me. What's more important is to pay attention to the other end. It's best to consider filling up not too long after it gets down to 2 bars. That way running out of fuel is never an issue and your driving remains stress free in that regard..

 

To give you an additional point of reference I had the opportunity to really watch it yesterday. Filled the car up in Mohave Valley, AZ and headed back home on I-40. The first bar didn't come off the gauge until we had gone 146 miles, passing through Barstow, CA on the I-15. The second bar came off 21 miles later. The top end on these gauges are extremely inconsistent. That's why I just fill up at two bars or 300+ miles driven and otherwise don't pay too much attention to the gauge. You'll get more comfortable with it over time.

 

Yes, the inaccurate fuel gauge can be maddening. On road trips I've gone 200 miles without losing the first pip. Now I always buy fuel at 420-450 miles since the last tank. I've put in anywhere from 8.5-9.7 gallons.

 

nice, thats good to hear. I over filled a few times and it seemed to sort out my issues. At about 370miles on the tank it pretty empy and I can get in 7-8gallon. Ive never gone much beyond 400 but that sounds about right compared to my normal cars.

My 4runner even with the gas light on I rarely get over 15gallons into the 18.5 gal tank. I think we just notice the issue more on our cars since the tank is soo small and we are always going for record mileage and distance per tank.