Question about gas indicator.

Same as with the battery indicator, one bar represents a range of "fullness". Cooling the gas in the tank overnight can easily drop you one bar if it was close to dropping one anyway.

 

The actual gas gauge is your most accurate measure. The range projection is based on current AVERAGE MPG and changes daily.
There's nothing "inaccurate" about the gas gauge, it's just that each bar represents a range of capacity and has limited functionality compared to an analog meter.

 

cruising range is based on past performance, just like ev range. it's only accurate if you drive the same way all the time. how can the car know if your next 300 miles are uphill or downhill? 25mph or 75 mph? a/c on high or windows open?

 

That's a dangerous assumption. You are assuming the gauge is linear. I don't think it is. In fact I'm sure it isn't even if it was intended to be.

With one bar left better get gas ASAP. If it starts flashing get gas immediately!

 

It can even change while you're driving, if you're going up or down a hill for a while. The actual measurement fluctuates a huge amount, as seen with a ScanGauge, as the gas sloshes around inside the tank. The car applies a lot of smoothing to that data before displaying it as the fuel gauge. Parking on a slope (up/down/left/right) might contribute to it being different when you turn the car back on.

And yes, it is very non-linear. The first pip is usually ~2 gallons or so, and the last flashing pip has been reported to be about 2 gallons as well; with 7 more pips to cover, that means there's only about a gallon or so for each other pip, even if they were all equal. (As an aside, cell phones do the same thing; they show 5 bars of reception for probably about half of the possible signal level, and don't start showing fewer bars until the signal quality starts to really degrade. In both of these cases, it has some psychological effects - making you not worry about getting gas/making a phone call - as well as the beneficial effect of giving you a more precise indicator when you need it most.)

 

It has looked to me, recently that when the gauge got all the way to the bottom, like no bars, I still has about 2 gallons of gas left - based on the amount of gas it took then to fill the tank.

Allen

 

Couldn't I use the trip meter to estimate the amount of gas I have left? After each fill up, just reset the trip meter and I should be able to calculate how much fuel I've used based on miles traveled and mpg, right? When it gets closed to 11.5 gallons, I better go get more gas.

 

I read somewhere that it's actually 11.5 but the spec is 1 gallon smaller. I guess we would never know until we push it to the limit.

 

Overnight the fuel cools down and the fuel vapors inside the fuel tank/line may escape or re-condenses into liquid form which will change the fuel gauge readings.

 

Wrt to specs, both the PiP(10.6 gallon) and Prius c(9.5 gallon) have smaller gas tanks than the Prius liftback/v (11.9 gallons ) . u can add about 1 gallon more of gas by overfilling it (gas goes into the vapor pressure release valve/line which can lose the *extra* 1 gallon of gas via spillage or by thermal expansion) which is not adviseable unless you are going to on a road trip (+60 miles/trip) and expect to burn that one gallon of gas that same day.