Once the fuel gauge bar thing is on E, the tank still has 2 gallons of gas left?

On my Gen III, I always have AT LEAST two gallons, when it says I have 0 miles left. There is a buffer. However, some have reported much less. Just become familiar with your vehicle. Over time, you will know when to fill up.

 

It's not a "hidden" two gallons, and the amount is certainly NOT guaranteed. The fuel sensor will reach the bottom of its' travel -before- every last drop of fuel can be pumped out of all the nooks and crannies. They keep the sensor -above- the bottom of the tank so it doesn't wear on the tank. It -might- be two gallons. It might not.

Good plan to fill up before it indicates empty. You DO NOT want to run out of fuel. It's dangerous for you (traffic or stranded in a bad part of town at the mercy of questionable individuals) and dangerous for the car. The fuel pump is cooled by the fuel.

 

I hope you're not thinking of the the sketch I posted with the secret reserve tank, lol. That was completely tongue in cheek.

For real low stress, fill up any time you're below half and passing by a station.

 

The stated tank capacity is 11.4 gallons, right?

When your gas gauge was down to zero, how many gallons went into the tank when you filled it up?

Not exactly sure what that will tell you, but its got to mean something!

 

It's intentional designed to give you some leeway. Almost like setting the alarm clock early earlier to get on out bed on time.. then we figure it out and snooze it till it last minute..

 

My first fill was 11.339 gallons at about 45 miles past zero range.

 

We won't know what the low fuel displays and warnings really mean until someone runs this new Gen4 model completely out of fuel, dead on the roadside, while keeping track of the distances and displays along the way and reporting how much refill fuel it takes.

Bob Wilson intentionally ran test this multiple times on his Gen3: [WARNING] Running out of gas (Gen III) | PriusChat Such experiments are not for everybody, and should not be run in challenging or risky conditions, nor when one is on any sort of schedule that doesn't allow plenty of time to recover from significant unexpected 'challenges'.

Whoever runs these experiments should be prepared for greatly different behavior than was reported on the Gen3. E.g. the Gen3 went roughly 100 miles past DTE (distance to empty) = 0 miles (Bob's reported distances actually measure from an earlier mark, the flashing pip). But the Gen4 behavior reported above blanks out DTE under 40 miles, similar to my new 2014 Forester that blanks out this display under 30 miles. But that Forester has essentially zero miles of cushion, I actually had it run out of fuel at approximately the point that DTE would have been Zero had it not gone blank (+/- a few miles, its DTE is always rounded to a multiple of 10 miles). (Conveniently, this happened seconds after I already pulled up to a fuel station, after wimping out about running the next road stretch, so I didn't need to pull out the spare can of fuel. That vehicle has plenty of other low fuel warnings, so no one can claim that it was a surprise. )

 

what does the manual state? should be separate quantities for main and reserve in the capacity's section.

 

There's one tank, AFAIK.

 

I am a fan of VW reserve and motorcycle reserve valves.

Bob Wilson

 

Manual just says 11.4 on page 729.

 

I do not know about Gen 1
Gen 2 had a variable sized tank that some times ran dry just 7 miles after the last pip started blinking. (Other times I had 30 miles) Toyota had many angry owners who expected to drive on empty longer than 7 miles. SO they made sure that Gen 3 had plaanty of reserve gas at E. It would not surprise me if the Gen 4 was the same. Until you get a 15 gallon gas can and run out on purpose, no one will know.

No modern car should habitually run out of gas:
Fuel injection assumes no air in gas, it will go lean and burn pistons.
Electric fuel pumps in the gas tank are cooled by the gasoline, run dry and they can over heat.

The Prius computers do not register adding less than 3 gallons of gas at a time. Smaller gas cans will not ever let the tank 'fill'
Running an out of gas Prius until it won't go will drain the HV Battery, not even the dealer has a charger for that; they have to get one from regional, so you will be on foot for a while.

Some folks do deliberately run dry ONCE just to find out. Just do not make a habit of it.

 

I ran my 2004 out of gas on two occasions, both on purpose. Both times I calculated that I had used about 2.4 gallons after the flashing pip started. On the Gen 4 Eco, based on the average tank FE, driving 45 miles past DTE is about 0.6 gallons. Subtract 0.6 from 11.34 when I filled gives you about 10.75 gallons from the top of the filler tube to DTE.

I read somewhere that the Eco has a 0.5 gallon smaller tank than the other models but can't find that reference at this time.

 

Some Prius drivers play a silly game called, "How low can you go?", or "How many miles per tank?" These are useless metrics which serve only to increase the probability of getting stranded on (or close to) the side of the road. For me, 'miles per gallon' is the one I like to keep track of. When the tank gets down to ~2 pips, I'll fill up. No muss, no fuss (perhaps because I am older and prefer peace of mind.) My two cents.

As far as the OP's original question, I'm sure we'll find out soon enough how much, if any, there is of a 'reserve' in the Gen IV.

 

there are not two tanks, but i recall a manual stating x gallons to last flashing pip, and x gallons in reserves or safety.

 

There are legitimate reasons to have a more realistic idea how much fuel range a vehicle really has, as numerous people who remember the 1970's fuel shortages and gas rationing can attest. Or aircraft pilots, many of whom wouldn't tolerate the multi-hour gauge uncertainties built into many common cars. Or people who often drive through areas where fuel is seriously overpriced or simply not available:

gas163mi2.jpg by fuzzy1 posted Mar 13, 2014 at 9:27 PM

DSCN1334gas106c.jpg by fuzzy1 posted Mar 22, 2014 at 10:15 AM

gas150km.jpg by fuzzy1 posted Oct 14, 2012 at 7:01 PM

That said, for common ordinary conditions, remember this guideline, ripped off from JimboPalmer's past postings:
With your mother-in-law 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.
With you spouse in the car, fill up at 2 bars. She will never let you forget that you ran out of gas and stranded her.
With just yourself in the car, fill up a 1 bar. Nobody else ever needs to know that you ran out of gas and got stranded.

 

Wondering if you have ever owned a Gen 2 Prius?

 

No, so I didn't have to mess with the "guess" gauge.

 

That capacity beyond the reserve wasn't as big with gen-1 and consequently, there were a number of reports of ordinary drivers running out of gas. It was a quite surprise to discover the American mindset was to routinely push extremes. Toyota adjusted accordingly. Very few run out of gas following that.

A major contributor to the reason for such a buffer is battery well being. In normal operation, there's a buffer for it too. Never deeply discharging is how it is able to last so long. Unfortunately, owners would drain the battery well past that longevity threshold. Consequently, its life is shortened upon continuing to drive after there isn't any gas available.

With such a long driving range anyway, why anyone would disregard the visual & audio refill warnings is beyond me. Why take the risk What's the benefit?