I ran out of gas @ 460 miles getting 46.5 mpg

The tank capacity is 11.9 gallons gross. The net capacity is less. The owner's manual explains this in more detail, but I usually assume I have 10 gallons of usable gas. It's probably a bit more, but then I don't have to worry about it. The Prius also includes a nifty little gadget called a gas gauge which gives the driver some idea of the remaining fuel. When it gets down to one pip, get gas.

Tom

 

How do you know you had three gallons remaining? There is no way to tell, short of driving until you run out of gas. The U.S. version of the Prius has a gas tank bladder that takes up a variable amount of tank space, depending on such factors as age, temperature, and the phase of the moon. You just can't tell, so it's impossible and foolish to try and make any assumptions based on presumed capacity and mileage. If you search this forum you will find hundreds of postings relating to the gas tank bladder and the "guess" gauge. You may not like it, but that's the way it works on the U.S. Prius. Caulk this one up to experience, and don't let it fool you again, now that you know better.

Tom

 

It has been discussed for some time on this board that the Prius's gas gauge is extremely inaccurate. Some have even mentioned a flashing idiot light simply indicating you have "x" amount of fuel left would be more informative than the present gauge arrangement. Whether by intentional design or simply poor design is unknown.

Many report going up to or over 200 miles before the first pip is gone. The remaining pips go at a quicker than normal rate and at one PIP it is anyones guess how much is actually remaining.

And although the fuel tank is specified at 11.9 gallons, with the fuel bladder coupled with how fast or slow you fill the tank in addition to outside air temps drastically affects how much fuel one can actually put into the tank during fill up.

Don't bother complaining to the dealer or Toyota, it will simply fall on deaf or ignorant ears.

Rick
#4 2006

 

It's the bladder. I've had my Prius since April, so I'm still getting used to the effects of colder weather on the car, but I'm definitely noticing a difference with the gas tank holding less in the cold. I've made a couple of long highway drives in the past month and have managed to get the same mpg as I was getting in the summer (by driving slower and keeping the heat off as much as possible), but I still needed to get gas more often than I used to. It's just not taking as many gallons as it did when it was 50 degrees warmer outside.

Also it seems that the gas tank will hold more if I fill it up sooner, e.g., getting gas at 5 pips instead of letting it get down to 2 or 3.

 

After reading your post from 12/13 http://priuschat.com/forums/showpost.php?p=531574&postcount=26 , I realize that had I seen it at the time I could have predicted this would happen to you. You post at the end of a long discussion that explains that you CANNOT count on 11.9 gallons of available fuel, and that you don't know how much fuel you have available. In your post you state, "I could have driven another 150+ miles after the flashing PIP". That's just a disaster waiting to happen.

The car told you it needed fuel. You chose to ignore the car because you thought that you knew how much fuel was in the tank. The car was right, you were wrong.

The fact that the car ran out of gas doesn't necessarily mean that the MPG displayed on the MFD is wrong.

There are a copule of possibilities here:

1) You forgot to press the "RESET" button the last time you filled up and the MPG displayed is actually the average of your past few tanks rather than of the current tank.

2) You put less than 11.9 gallons of fuel into the tank the last time you filled up. Due to the stiffness of the bladder and variations in gas station pump sensitivity, perhaps the pump shut off when you only had 9.9 gallons in the tank.

3) The MFD is generally accepted around here to be 2% or so inaccurate, so if it displayed 46.5 MPG, it is entirely possible that you were actually getting 45.57 MPG. This would indicate that the last time you filled the tank the pump shut off when you had about 10.09 gallons.

Do you have your receipt from your last fill up? How much did you put in? I'll be curious to hear how much you get into the tank this time. Perhaps you'll finally come to accept what everyone here has been saying.

"Unless the tank was dry to start with and you added 11.9 gallons yourself, you don't necessarily have 11.9 gallons of fuel in your tank when you fill it. As a matter of fact you most likely have less than 11.9 gallons. How much less? Because of the bladder, the gas station pump sensitivity, and other factors, YOU DON"T KNOW so don't try to predict remaining fuel or remaining miles based on MPG."

"When the fuel gauge starts flashing, you really should get to the nearest gas station. Sometimes you might get lucky and have the gauge start blinking early so you actually can get another 100+ miles, other times the gauge might wait longer to start flashing, and you may have less than 30 miles to empty. Since you don't know how much fuel you have to work with, driving while the gauge is flashing is AT YOUR OWN RISK and you really only have yourself to blame."

See also:
http://priuschat.com/forums/showthread.php?t=33751&page=10

 

11.9 is the maximum capacity of the bladder tank, and you won't come close to that in winter time. IN addition, there's the winter gas mixture.

Regardless, you were driving around for a long time on a blinking pip?? What were you thinking? GO BUY SOME GAS!!!

It doesn't matter how much you could put in the tank after you ran out, or what the capacity of the tank is, the only thing that counts is how much was in it when you started the tank for calculation purposes. Actually 46 mpg in winter time is not that bad. But why push it? Get gas and done run out. If you want to work that hard on a good mileage tank, don't wait until the last pip. Start when you drive off from the gas station.

 

In winter I count on 9 gallons of usable gas. In the summer 10. Period. The bladder gets stiffer in new cars and in winter. You apparently have both. When it gets to one PIP get gas. If it starts flashing get gas NOW. I fill my tank when it gets to 2 PIPS personally. I don't bother with how many miles I went on a tank because to me it's not worth it.

 

I also assume 10 gallons and if you assume this... you are getting aprox. what you say you tank lasted...

and 460miles/tank is pretty good compared to most vehicles out in the street.

 

Yeah I agree, this is nobody's fault but your own. When the pip is flashing...it needs gas irregardless of how much you've calculated you have remaining in your head.

When my normal car with a normal tank and an analog gauge gets to "E" I fill it up with gas. When the Prius' last pip blinks, fill it with gas!. I guess you found out that you only pumped 10 gallons into that 11.9 gallon tank huh?

To blame it on the car is assinine.

 

The correct way to determine your MPG, is to divide the number of miles driven, by the number of gallons of gas you have REPLACED.

In other words, you cannot tell the MPG until you refill the tank. Do the math. This will tell you how that tank's MPG was.

Keep a log book of your gallons and miles. Over time, you will find out what your average, or "Lifetime", MPG is. Ultimately, this is the important number, not any one individual tank's MPG.

 

correct... when it flashes just fill it up... I put in 10gals aprox each time I fill but if it flashes sooner than expected I simply fill it again.. I like to play it safe...

 

OMG, I cant say what I think because it will get me banned.

 

I'm a newbie and I'm only on my 5th tank. It seems to me that the lifetime mileage is the way to go. On my third tank the computer said 48 and I calculated 39. I obviously was able to put more gas in on that tank then I did previously even though I attemp to be consistent with how I refuel as far as the pump shutting off. On the next tank I got 50.2. average lifetime now is around 48.

Having said that and given the obvious limitations of the cars fuel guage, it still seems silly to run out of gas when the car is telling you it's almost empty. The car is a machine. It doesn't care if you're right.

 

I've run out of gas in my 2004 Prius during the cold heart of winter as well, and when it happened, I calculated I had used 10.5 gallons. However, I was prepared for it, as it actually says in the manual that you'll have less tank capacity during the winter.

Sorry to hear that this happened, but it's not surprising at all.

 

Ditto.

Please tell me you are not an airline pilot.

 

One of the many things I learned on this site is for god's sake don't run out of gas in this machine. It gets very unhappy. Have seen so many posts concerning people trying to get 50 miles out of the last flashing pip and end up with a tow to the dealer. How about the one guy who ran it dry and complained that it wouldn't go over 70 mph's on emergency battery? I think he ended up damaging his M/G's too. When it hits 2 pips I hit the gas station. I was convinced the car is a little different when I saw I was getting almost 80 miles on the first pip.

For the newbs headed to the dealer on the end of a tow hook:

Put gas in when it hits 2 pips. Gives you a chance to laugh at other people
putting 20 gallons of gas in there car.

Put gas in very slow. That way gas won't splash out and contaminate the plastic zero vapor emssions bladder. Another dealer headache. I cut a little block of wood that jams the gas handle in at the slow mark. Takes a few extra minutes at slow fill but so what. Use it to walk around the car and look at the tires. When the gas pump clicks off the first time do not top off. Again so you don't spill gas into the BLADDER. I know it goes against everything you have done all your life but its a new different car. Embrace it...your helping the environment.

And read the manual. Its a must read for this car. Read it twice.Ask the experts here if your not sure what certain things mean. I'm no expert. Everyhthing I have learned here is by looking over the shoulders of people who really know this car. 75% of all posts here can be answered by reading the manual.

That is all.

 

I have only filled up the tank 4 times. But each time I waited for there to only be 1 pip left on the screen. Each fill up took around 8.2 gallons- 8.9 gallons. Cold weather does effect the bladder.

It's dumb to think the screen is wrong though.