Gas gauge showing some left, then jumping to 0

it's not that accurate. that is not the gas gauge. the gas gauge is the column of horizontal bars.

either way, a young woman should fill the tank at half empty or so. teach her now, not to drive around on fumes, before she gets stranded somewhere dangerous.

 

13 miles range on a warmed-up car that gets 40-50mpg is almost empty. The "guess-o-meter" has to recalculate once the car cools off because a cold engine needs a richer fuel mixture (more fuel) to run properly = lower mpg in the short term.

Take away is to train your daughter to refill the tank before it gets anywhere near that low- otherwise she WILL run out of gas (that's bad in general, but can be $$ on a Prius if she then tries to drive it and kills the HV battery as well).


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Your daughter's observations appear normal. This displayed DTE figure is just a guestimated forecast with some built in safety margin, and is necessarily crude because it can't know or adjust for future driving conditions. MPG varies drastically depending on differing conditions and cold starts vs long warmed-up trips.

MIne can snap to 0 any time it is showing under about 25 miles. When I was watching it (which is infrequently, and not recently), the bigger jumps down happened when climbing hills. It can go lower without snapping on flat ground in continuous warmed-up driving. The lower the number goes, the more likely it is to snap down at any moment

Do know that when this happens, it has roughly 2 gallons of reserve fuel left. But there are no additional warning levels beyond this, until the car runs out of fuel, so don't push it far. For more details, read just the first post of this much-too-long thread:

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

I have driven only about half as far after the last low-fuel warnings as Bob did. I didn't run it all the way out of fuel.

Other notes: My Subaru rounds its Distance-To-Empty display to the nearest 10 miles, not 1 mile like the Prius. And the Subaru blanks out this display, showing just dashes instead of a number, after it drops to 30 miles. It has no built-in reserve, but does have multiple other low fuel warnings that Prius lacks.

While my Subaru DTE is based on a much shorter drive history and can increase very significantly when driving conditions improve (i.e. going downhill after an uphill), the Prius DTE never ever increases without detecting a significant amount of fuel added. 1 gallon is not enough. And even in the very best MPG conditions, gliding downhill with no fuel consumption for very long distances, DTE is still forced to decrease at least 1 mile for every 2 miles driven.

 

yes, let us men grace the dte = 0 miles to drive 30 more miles, then fill up.

 

Nothing is wrong with the car. But many people have much greater accuracy expectations for this dumb forecast guesstimate than it can reasonably deliver.

Killed batteries from continuing to drive on the battery after running out of gas, are a Gen2 (and maybe earlier) problem. Gen3s are much better protected from battery damage, so OP and daughter don't need to worry about that issue.

But Gen3 lacks the clear dashboard warning of having run out of fuel that Gen2 had, and keeps silently driving (on limited electric power) until it gives an Electric Power Steering warning. For details, see Bob's thread linked in my earlier reply.

Jimbo's old advice -- to male drivers -- is still somewhat relevant here. It goes something like this (my paraphrase, don't remember Jim's exact words):

* When your mother-in-law is in the car, fill up at 3 bars. She will never let anyone she knows forget that you ran out of gas and stranded her.

* When your spouse is in the car, fill up at 2 bars. She will never let you forget that you ran out of gas and stranded her.

* When you are alone in the car, fill up at 1 bar (before it starts flashing). Nobody else needs to know that you ran out of gas and got stranded.

 

Sounds like the Distance To Empty guesstimate gauge?

I would rely on the gas gauge, the one that shows 8~10 blips, representing the (very approximate) amount of gas in the tank.

and yeah, if it’s below 1/2 and a gas station is convenient...

 

this has nothing to do with the accuracy of the gauge and everything to do with slosh.

you have 2 1/2 gallons (or less) in the tank. the needle says 1/8 left. the guestimated range says 15-45 miles. then you start moving and the fuel sloshes forward/rearward. the gauge can't tell what's happening, so it changes.

btw, it's a really bad idea to leave the house on 1/8 of a tank, especially if it's a new/inexperienced driver.

if you're sending unit is failing, you'll get wild swings in readings also.

 

Totally agree with filling the fuel tank earlier than later... But I did notice some problems with the fuel gauge on my car.

It is on my 02 Prius C (not Prius). Sometimes the gauge stays on 3 or 4 bars for a longer time than it should, then suddenly drops to 1 bar. On the contrary, the Distance To Empty guesstimate is more reasonable when this happens. To make it more confusing, this only happens occasionally.

I brought the car to the dealer, and they said they recalibrated it, and didn't find anything wrong.

But this still happens from time to time.

It taught me not trust any single indicator too much. Instead, using a combination of distance driven, fuel gauge, and miles left to judge when to refill, and refill early.

 

what about the use of air conditioner also since weather is getting warmer? And the cold soak start up for ICE to get warm?