How much gas in the tank?

When the last PIP is flashing, you have about 2.1 gallons left in the tank. Source =

[WARNING] Running out of gas (Gen III) | PriusChat

Another, very simple, way to estimate your tank range is to multiply your displayed tank mpg by 10. Thus, if your displayed value is 48.6 mpg, you should be able to go 486 miles and then look to fill up. If you filled up at 486 miles, you'd find that your car would take about 10.5 gallons of gasoline (11.9 gallon capacity), leaving a 1.4 gallon safety margin. This assumes that you had a proper fill up and the gas station fuelling pump did not shut off prematurely.

My data also suggests that your true range is about 11x your displayed value. Thus, in the 48.6 mpg scenario, you could probably drive 534 miles before running out of gas. Again, this assumes a proper fill up on your previous fill up. Personally, I would never push the car to the 11x limit. The 10x limit is a nice, simple estimate that will keep your heart from needless palpatations when the last PIP is flashing and the DTE (distance to empty) = 0.

Driving on a tank, low with gas, shouldn't harm the car. Driving the car and running out of gas can cause problems (premature wear on the fuel pump), plus will flash an error code. The dealership can charge you to "read" the code and reset it and may be able to use that information later (say if your fuel pump burns out) as evidence of customer abuse rather than a faulty part.

 

From what I gather, once your car beeps at you and the last pip starts flashing, you've got less than 100 miles to go before you're out of gas. This of course depends on your driving habits.

Typically, when my last pip starts flashing, I give myself my current Cons. to find gas. (For example if it beeps at me at 480 miles and my current Cons. reads 54, I know I want to find gas before I get to 534). This also usually gets me pretty close to the 10x rule Codyroo mentioned above.

 

10 bars in the graph, 12 gallon tank, close to 2 gallons left when the bottom bar blinks = approximately 1 gallon/bar. I did my first fill when there were 5 bars showing, 4.7 gallons the calculation seems to make sense. Imagine a gas gauge that actually means something.

 

I average about 42 MPG b/c I have the 17's and I drive a constant 9 over on the HWY. I wait until the bar flashes, then reads zero miles 'til empty, then count to 50 miles. Never run out of gas so far. The most gas I was able to put into the Prius was 13.02 Gal. Lost of 12.5's too.

 

Does the Five have a bigger tank? I though the tank was 11.9 gallons.

 

The tank is 11.9 gallons. There are differences in tank size tolerances (someone posted a link but it is something like 3 - 5% difference in tank capacities). However, in aarethas' case, I suspect that after the pump shuts off, he manages to pump in another 1 to 2 gallons.

 

All very interesting. And unnecessary. I just look at the gas guage, and if it looks low, I fill it up. I never run out of gas.

 

Its not about running out of gas. Its understanding the numbers. Engineers like that sort of thing.

 

I know all about engineers, my father was one. Everything was over analysed and always took longer than necessary.

 

Actually I probably didn't take long enough in purchasing the new car. I guess I'm making up for it now

 

Scientists like this sort of thing too.

 

My father was not an engineer, so I witnessed many scenarios where the fixes and recovery efforts took longer than an initial overanalysis would have.

 

This will vary from pump to pump -- ideally they would all be calibrated the same, but some of the lock-stops release earlier and/or the pump itself is set to stop earlier. A second issue is differences in pump nozzle dimension / bend / neck clearance. I note how the hose pivot works as well, because some more rigid joints will put more twist on the nozzle and change how it seats in the filler neck.

Being aware of per-tank MPG and expected fill quantity is helpful -- if I expect to put in 11 gallons, and it stops out at under 10, then I will add some more. This assumes other variables such as climate, tire pressure and proper maintenance are controlled and not out of line, any one of which could cause a variance in MPG performance -- but these will most often result in needing MORE gas to fill than expected.

I concur with the prior suggestions that when the Prius first "beeps" and begins flashing the bottom pip on the gauge, you have appx. 2 gallons remaining, which will take you another 80 - 120 miles, depending on MPG. If you use the rule of adding your "Cons" to the current tank miles, and filling at or around that sum (e.g. from /Selzier 480 beep + 54 Cons = FILL by 534 miles on ODO), you'll be safe.

~Chris