Just an idea for a topic as I sit here and think about my nicely cooled car... surely I can't be the only Prius II owner who gets a bit irritated at the gas gauge. I just filled up again (ha) using only 6.34 gallons. This is with the gauge showing two bars left. Anyone else have this annoying glitch? I wouldn't mind, if it weren't for the tank holding 12 gallons, supposedly.

 

2 bars left is quite a bit, my friend's Prius will go for over 100km after the last bar starts blinking!

There have been some problems with the tank, bladder and guage, but I think you might just need to get used to the way it measures fuel.

 

The pump typically stops for me after about 8 gallons although I use about 9. Funny how that works out, isn't it. Something's not right, there. It's annoying to know there's unusable room in that tank, but what can you do? I even had a service where they replaced a computer and part of the tank but I didn't even notice a difference afterwards.

 

I think the best way to describe the gas gage on the Prius is nonlinear. If your commute is like mine, about 10 minutes with no highway time and a number of lights (I bet there are very few here that can share that experience), then you often find that the fuel gage hovers on a pip for many days (more than a week) without droping, and then it will drop 2 pips in a week and then hover again. I've been hovering on 3 pips for at least a week and half now and I keep wondering when it will drop to 2 remaining.

As a general rule, I fill up at 2 pips regardless of how many miles I have traveled or how much farther my average indicates I can go. I get between 7 and 9 gallons of fuel into the tank when the gage shows 2 pips.

 

I keep trying to figure out my flaky fuel gage. I can't seem to find any consistencies with when/if the fuel gage will show close to true at the end of a tank. Sometimes I'll be turning 550+ miles on a tank when the add fuel warning goes off and sometimes I'll only be at 400. I keep trying to relate the behavior to temperature, driving conditions, and phase of the moon, but I just can't seem to draw a correlation. I agree with JeromeP that the gas gauge is certainly not linear. I generally hit 130 - 150 miles on the tank before the first pip disappears. By 1/2 tank the pips have aligned to about 55 miles per pip and continues that way through the last 3 where I tend to either get huge mileage on the 7th pip or a rapid progression to empty.

Maybe what we need to do is start gauging how much fuel is being consumed per pip in our vehicles. Maybe we can get a few volunteers living in metro areas, where there are gas stations on every corner, to start mapping pips to fuel volume. I propose filling from the different pips 3x to look for consistency. Start with 1 and work your way down. Anyone else have an opinion on what other data we should keep beyond gallons and miles? How about ambient temp?

 

Have you ever noticed that you are most likely to lose a bar on the fuel gauge when you are going up hill but you never ever gain one on the way back down? For me, the cuplrit for flaky behavior is hills. Every time I go up a steep hill I pay close attention to see it the reading changes. Often it does. My guess is that going up a hill, the tank sensor detects a lower level due to movement of the fuel to the back of the tank. Usually when that happens, the next bar lasts much longer, unless I have another steep hill. Invariably, I get the ADD FUEL warning while going up a hill. And the one time that I actually ran ran out of gas. Well I'm sure you can guess.

 

My girlfirend has a totally digital dash in the Yaris (Echo). Give me traditional needle dials any day - especially on the speedometer, I like to see where I am on the gauge, not just a number.
I remember when the 4th gen Honda Prelude got a digital dash in the 90's and everyone wowed, probably something to do with Knight Rider

 

The Guess, uh Gas gauge on the Prius is the biggest joke I've seen.
Not only is it not linear, it's also not consistant.
Thought I finnaly had the SOB figured out after 15 tank fulls.
Like clock work. . .
10 >9 = 110miles = 2.2gal
9 > 8 > 7 > 6 = 30miles = 0.6gal/bar
6 > 5 = 40miles = 0.8gal
5 > 4 = 35miles = 0.7gal
4 > 3 > 2 = 55miles = 1.1 gal/bar
Fill up just after 2nd bar ~8.3 gallons each time ( that was from april 1 to 2nd week in july)
Since the temp went up to the 90's, the bars (9>6) that were 30 mile now are 40-50 miles but the bars that were 55 miles (3 & 2) are only 25-30 miles.
Fill-up is still the same though (~8.3 gallon).
My guess is the bladder is expanding more, due to higher temps and weight of gas.
Can't figure out the decrease at the 2-3 bar though.

 

There is definitely a problem. My gauge was right at half full when I turned it off for the night, the next morning it was sitting at two bars. I was worried since I had over 250 miles to drive so I stopped to fill up and it would only take 3.6 gallons. Now for a 12 gallon tank that is not right. After the fill up the gauge never hit full it only went to the first bar over half full.

 

Could you provide us with some information about your vehicle? Model year, how long you have owned it and any of your previous experience?