How much gas are you able to pump into Gen3 when empty?

Well, tbh, according to people smarter than me, it isn’t advised to get the fuel that low as it makes the fuel pump work harder and wear out sooner.

That being said, I pushed it (with a gallon can in the back just in case) to 11 gallons but don’t plan on ever doing again. My usual fill-up is 8-8.5 gal unless weather is a factor and it pushes it to 9 gal.


-Spiral

 

You aren't really going empty. Bob Wilson intentionally has, many times, for a variety of engineering tests. Here are just a few of them:

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

My Gen3 Prius fuel gauges (2010, then 2012) are hands-down more consistent and linear than on any prior car I've ever driven. My Subaru is now a bit better, but it is also a newer design.

All but one of those prior cars had very significant range beyond the fuel gauge 'E' or the low fuel warning light. One had a huge amount of fuel below that point. The single car lacking a large safety margin, actually went dry on me with the fuel gauge still above 'E'.

 

I did 11.808 gallons last year when I did my 624 mile tank. That was 105 miles driven past the flashing pip. Even getting gas around the 0 miles to empty mark I average 8.9-9.4 gallons.

 

11.9 us gallon when empty.

 

Since I have had my Prius 2010 Model my MPG has been at 44-45 City, 47-50 Hwy. Up until recently things have been really good then I had the new software update and I swear on the hwy I cant get over 38 MPG. I went back to the dealership and they told me nothing was wrong that I should drive in ECO mode more and so on. I have lost 70-80 MPG per each full tank of gas. Any advice on what the heck is going on?

 

I've put that much fuel in once or twice.
After the last bar starts blinking, I take 125 miles as maximum remaining distance and then fuel up usually around the 100 miles.

 

This subject often produces angry replies from people who swear that only idiots try to extend the range, but I think it is is an important topic. When travelling a long distance, fewer pit stops mean arriving sooner, or maybe there is really cheap gas at a truck stop xx miles away and you want to figure out if you can make it or should stop short instead, etc.

One of my first threads was on this very topic: Summary of the Gazillion Fuel Left When Distance to Empty = 0 or Last Pip Flash and I got some "stupid topic" replies.

But mostly I came away with:

Not to high-jack this thread, but would anyone disagree with this statement:

"IN AVERAGE/NORMAL FLAT HIGHWAY DRIVING, YOU CAN ALWAYS GO 50 MILES AFTER EITHER THE LAST PIP OR DTE = ZERO"

 

Is this materially different than any other common cars? As in most drivers not usually using the last few gallons set aside as safety margin, regardless of make and model?

 

For the cars I've been driving over the past four decades, this IS the norm. The exceptions were my very first car, which ran dry while still above E, and my first Subaru, which had nearly a third of its fuel tank below E. The others before Prius had roughly 100 miles of margin. Post-Prius, my newer Subaru has trimmed that margin to about 75 miles, but with more warning stages.

100+ miles is totally ridiculous???

Do you drive only where fuel stations are always close? I don't:

 

The gauging certainty of fuel remaining until engine starvation has always seemed to be suspect.

On top of that, the 'distance remaining' calculation is merely a forecast assuming the MPG of the route ahead will be the same as a certain distance behind. I.e. future results will be identical to past performance. But that is often not true, for reasons the car cannot know in advance. Out here in the mountains, and especially in winter, that assumption is often hugely separated from reality. Climbing multiple thousands of feet requires far more fuel than running flat. Changing weather often brings wind or liquid precipitation that significantly reduces MPG, and sometimes solid precipitation that can hugely cut MPG.

I won't expect fulltime Florida residents to grasp the full extent of this elevation and weather MPG variability.

Many people are not good at the mental math needed to figure an accurate answer, and are woefully unaware of just how widely MPG varies over different conditions. Thus, absent a significant safety margin, the Customer Service lines and representatives would get a flood of angry customers claiming, correctly, "Your car said I had enough fuel to get there, but then it stranded me out in the middle of nowhere, at night, in a storm!!!!"

The best way to avoid those clueless but angry calls is to provide a substantial safety margin, more than enough so that customers know they have no one to blame but themselves.

 

The one that is smart enough to open up a gas station half way to the next station,
would probably make a lot of money.

 

Iskooi’s, I don’t disagree with your sentiment.

On another forum there was a discussion about headlamps and using LED replacement from Amazon. Part of the discussion included that a lot of R&D is spent on headlights and the telemetry of the light from the projectors, blah blah blah. Do we know that for a fact? Do they just have to design something that reaches x distance when a tweak here or there would go 1/4 mile further??

I guess what I’m trying to say, do we know if toyota pulled that reserve out of there nice person or did they have a legitimate rational behind it. Again from my other response, running low on fuel is said to make the fuel pump work hotter because it’s no longer submerged by a liquid that is acting as a cooling medium. So based on the dimensions of the tank, maybe toyota determined that those 3ish gallons is the safe level to maintain the pump. Can you go further, sure. /SHOULD/ you go further, not if you don’t want to potentially replace the fuel pump sooner.

Additionally, (and I understand your 30 min out of the way issue) but over the life of the car, you are using the same amount of fuel regardless at which point you decide to pump. If I fill up every 1/2 tank instead of gauge empty, I’ll only put 4.25 gallons which takes less time to reach filling than the 8.5 gal (which from the moment I pull off the main road to pulling back on for me is 5 min). So maybe more frequent fill ups I would spend more time overall, but it might only be a 2 min difference per 11 gallons fill time that you spend.

I hope that doesn’t come across negative, just a different viewpoint. Like I said, I did it once so I too would know if I could make it to that next station or not.


(*side note, when I see a sign that says next station 90 miles and I’m close to E, I’m one that stops because there’s no guarantee that 90 mile station is still operational)


-Spiral

 

A risk of running out of gas often is that you will assist in the early death of your traction (the big one). Last year my weak 12v battery made gas gauge go nuts and I ran out of gas car - did not know it- and drove until car came to a total stop. That time my traction battery survived the no gas torture. One gallon of gas and car came back to life.

Many episodes of running out of gas may damage your traction battery. In fact a big way to void the warranty on a traction battery is to have fault codes in ECU revealing you have ran car out of gas !

 

I looked up my old record on my Gen3. The most I put in was 11.01 gal.