Just bought 2007 Prius but confused about fuel gauge accuracy

Gen II Prius have a gas tank bladder than sometimes makes it hard to fill the tank to it's maximum. It also has an analog gas tank sender unit. The cars computer changes that to digital looking "pips" on the screen. Gen II users have learned to fill up when you have two pips to minimize the chance of a $1000 repair bill for a new gas tank. It looks like you have a unreliable sender unit.

 

Is gas $3.33 in LA? Up north in SF it's still $4.00 and above.

 

The Owners manual admits it does not register amounts under 3 gallons, yours seems to stretch that a bit. When possible, do fill ups. (You wish to never organize your life to see it blink. I have had as little as 7 miles of gas when blinking)

 

Some of use here call it a "guess guage," because that's more what it behaves like.

 

If you put in enough gas for the micro brain processor to recognize it IS accurate. It just has those "quirks", or perhaps "personality".
Last winter I filled up and it didn't change. The gauge didn't register fuel use until it got below the level when I filled up.
Now THAT'S personality!

 

Confused about "fuel gauge accuracy"?

You can't be confused about what doesn't exist.

 

let's be completely honest here...how many cars has anyone here actually owned where the gauges were accurate to begin with?

 

Well, it should be more accurate than that, you're definitely over-exaggerating that part. I like Jimbo's answer the best, I think it wasn't enough the first time to register that an upward change had occurred. (Was it really 4.5 gallons?)

There is some variation from one bar or pip to the next as to how many miles that represents (even assuming you're driving consistently in similar weather and conditions). One pip might go for 50 miles and the next one only 25 miles. The top one of course usually lasts over 100 miles, but that's normal. The bladder in the fuel tank will only affect how much is needed for it to fill up completely - in cold weather (never seen in south/central CA) you may only put in 7.5 gallons before it clicks off and in warm weather you can get maybe 8.5 gallons. (I refill after it gets down to 2 pips for a bit).

The best thing to do is just fill it all the way each time. I need to do that so I can compute my mpg more accurately, although keeping the car lighter (less fuel in the tank) should increase your mileage just a tiny bit. Not sure if it would be detectable, and so many other variables come into play it would be hard to prove.

xpcman - I believe your reference to the repair bill is when you -overfill- the gas tank and get gas into the charcoal canister, etc. If you run on empty that may affect the battery if you try to go too far on battery only when you run out of gas, but I think Toyota added protection into the system for that.

 

Can't the sensors be re-calibrated?

Mine has been quite consistent. After traveling 250 miles, I'm almost always at half-full on the "gauge". I always try to fill up at 2 pips, and usually get about 8.5 gallons in when I re-fuel. If I fill-up at 3 pips, it takes around 7 gallons.

I always reset the MFD and dash trip odometer (so I can easily see how far I've been with the MFD off). Around 400 miles is when I usually fill up, and that's when I have 2 pips left, which accurately shows that I have around 1.5 - 2 gallons left.