How many gallons of gas does Prius hold?

You're close. The official capacity is 11.9 gallons, but there's a bladder which will prevent you from completely filling the tank most of the time. Because of this, don't assume that each bar is one gallon. Heck, the first bar generally won't go away until 100 or so miles and then the rest drop pretty quickly.

We call it a "guess" gauge.

 

<_< Page 427 of your Owner's Manual. THEORETICALLY, your Prius' fuel tank capacity is 45 liters, 11.9 U.S. gallons, 9.9 Imperial Gallons... THEORETICALLY. Lot of helpful information in your Owner's Manual.

Due to the U.S. fuel bladder, the useable fuel is most certainly somewhat less than the 'capacity.' You might benefit from a SEARCH of PriusChat on "fuel gauge" or "guess gauge" or "gas gauge" to learn what practical fuel capacity is available. The bladder is susceptable to ambient temperature - stiffer when cold - which affects how much fuel you can pump. The stations' pumps vary as well, particularly as to back pressure required to shut the pump down, which in turn makes it problematical regarding how full you can fill the bladder.

 

Generally, when we fill up, we put in anywhere from 8.5-10 gallons, so we're usually refilling at some point after the 360 mile point. But the bladder system used by the Prius does mean that I just refill after the light starts blinking rather than relying on my miles since the last tank. We also don't try to top off or overfill.

If you want to get a good picture of how the gas system really works, you can see it taken apart in this thread:
http://priuschat.com/index.php?s=&show...st&p=419197

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 10:16 AM) [snapback]429000[/snapback]</div>

I'd guess you don't have about 5 gallons left.

My MFD is off by 2 to 5 mpg. In a high mpg car with a small gas tank like this, it makes a huge difference in what you really have to work with. Over 12 gallons, do I have 25 miles left based on math, or up to 60 miles left maybe?

When you're down to 1 bar left, fill up. If you ever get the blinking final bar, get real serious about gassing up and never count on a certain amount of miles left because you did some math based on some mpg number you think you are getting. The Prius fuel gage is about as reliable as the 10 day weather forcast.

If my mfd says I got 56, then I'll get 52ish at the pump. Instead of going 672 miles on my 12 gallons, I'll be stopped along the road waiting for a tanker truck at 624, a full 50 miles short of my favorite gas station, then take in to account I didn't really get all 12 gallons on board and I'm out of gas at 560ish... So, I rarely go past 550 when I'm stretching myself(maybe the bar is blinking at 550).

 

I tend to think of the bladder like a gallon bucket, with a mark at the gallon point. Put a brick in and fill to the mark with water. Is there really a gallon of water in the bucket? Nope, but if you were taking a picture of the mark alone, it would show one gallon. That's where the "guess" gage looks. The problem is that the "brick" will change size so you can't rely on it to be the same every time.

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 08:16 AM) [snapback]429000[/snapback]</div>

Welcome to Priuschat.
CAUTION:
You DO NOT have 5 gallons, although the guess gauge shows 3 pips.
The rule most Prii drivers follow is to fill up at 2 pips. Most probably you are going to put around 8 Gal. DO NOT try to top off; you have a good chance of getting gas all over you since the bladder will burp after you remove the nozzle.
Enjoy your new car.

 

If this is your first tank, wait until you have 1-2 pips left and then go gas up. Don't try to see how far the car can go!! The dealer fill means nothing because you don't know how much they put in there. Do a search on this topic and you'll get endless hours of entertainment.

 

Over TWO Prius and over 2½ years of Prius-ing, I have found the MFD MPG readings to be over 98% accurate when compared to hand-calculated MPG. For me, "That's close enough for 'government' work!" I have kept an Excel spreadsheet all those months for comparison and 'cost per mile' calculations.

Here's one added factor for your consideration. Most Prius owners have observed that the best MPG does not begin to become apparent until as many as 6,000 miles on the odometer, some have even reported gains in MPG for up to 15,000 miles or more. It may take awhile for your Prius to 'loosen up' and for you to develop different driving habits with the unique nature of the Prius.

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 11:37 AM) [snapback]429053[/snapback]</div>

Read these posts more thoroughly. While with Prius is listed with an 11.9 gal tank, it actually uses a rubber bladder. The bladder varies in size with outside temperature. You can't accurately calculate your mpg based on the assumption that the car contains 11.9 gals of gas, because even at full it most likely doesn't.

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 11:16 AM) [snapback]429000[/snapback]</div>

Do a search on PriusChat for the phrase "out of gas" and see how many other people guessed the same thing and were wrong. The list of people who attempted to out-guess the gas guage and failed is quite lengthy.

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 01:10 PM) [snapback]429083[/snapback]</div>

that calculation is incorrect. Take this scenario: It is freezing cold, and you fill it up. The bladder doesn't expand, so you don't fill it to the top.

The next time you fill up the gas, it is burning hot. And you put in a lot more then before because the bladder is flexible.

 

After filling up my 2007 Prius, and a recent trip to Palm Springs from the West San Fernando Valley in addition to driving around to misc. hot spots while in Palm Springs, I was able to travel 147 miles on the first bar equating to 55.1 MPG combined City/Hwy mileage. Not Bad! My average is 52 MPG on a regular basis here in the Los Angeles area both City & Freeway driving. I can hardly wait for the 3rd generation Prius!

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 10:10 AM) [snapback]429083[/snapback]</div>

That is exactly how you should do it on a normal car, but the bladder makes getting the same level in the tank very difficult (maybe impossible) to do.

My observation from about half a dozen fillups is that an individual tank may vary a lot compared to the MFD calculation, but an average of several fills seems to agree reasonably well with the MFD.

 

<div class='quotetop'>QUOTE(dnoh @ Apr 24 2007, 01:00 PM) [snapback]429027[/snapback]</div>

If you wanted to figure your MPG off the first tank, you should have filled up right after you bought it, so you would really know how much gas you used for distance travled. The dealer didn't truely "fill-up" the tank and you don't know how much gas you used. Forget about that first tank. Fill it up, reset you odometer and consumption screen and try it again this time.

Learn how to feather the gas pedal, especially going downhill, and shut that ICE down intentionally and then reapply enough pedal to get yellow (electric power) arrows only. Your MPG will soar.