The Prius Bladder/Guess Gauge... For Dummies! (with easy-to-understand-illustration)

The tank theoretically holds 11.9 gallons. In reality, it holds about 9.5, +/- one gallon.

 

Sometimes, but seriously, either you chose not to look at the pictures and read the posts, or you are intentionally choosing to instigate and antagonize.

Assuming your car was originally sold in the U.S., you are mistaken in assuming that your tank has 11.9 gallons in it when it is "full". Therefore your simple math is incorrect.

The bladder generally holds less than 11.9 gallons, and then it can fluctuate by over a gallon depending on temperature and other variables.

 

The tank doesn't hold 11.9 gallons, if you have the U.S. version. That is the whole point of this thread, plus a nearly endless number of other threads about the "guess" gauge.

As for being adversarial, not really. We do get a little short sometimes when people post without reading the rest of the thread.

Tom

 

I think the first post was top notch, tha tank may well hold 11.9 gallons (what ever they are) but the BLADDER has a variable capacity between 8 and 11 gallons which is dependant on several factors like the ambient temperature and the temperature of the fuel, the pump, the status of the HSD system when filling (if on it will be a pig to fill).
No one is arguing just stating the facts. If you had 3 gallons left why did the car stop after the fuel gauge said it would?

 

Naah, we just want you to feel welcome !
We've all made the same presumption, that's how we know it's easy to presume you're filling to the same level(s). That said, we do have our share of fun here so, welcome.

 

The fuel tank's internal bladder means that the actual capacity is (1) variable, and (2) almost always less than 11.9 gallons, sometimes quite a lot less. One cannot reliably calculate how much fuel is in the tank at *any* time, with the exception that when the last pip starts to flash it is about to run dry. (Some posters have been familiar with this for a long time and perhaps forget that none of us were born knowing it.)

This is a North America thing only, to accommodate US rules on hydrocarbon emissions. Other geographies get fuel tanks without internal bladders and have less uncertainty.

 

I think we made our point. He'll either

A) realize we call it a "guess gage" for a reason, or

B) insist that the tank holds 11.9 gallons, go down to one flashing pip, say, "Hey, I still have three gallons left," try to go another 100 miles, and learn his lesson that way.

 

I think the only way to know, with greater certainty, how much fuel is remaining is to run the Prius down to empty, and then top it off. You'll have a good idea how much fuel is left, based on your current economy and distance driven. Before CAN-View, i'd multiply my current tank's trip and current FE readout to figure out how much fuel is consumed. As long as I consumed less fuel than I filled up with, I'd knew it'd be okay.

BTW, my tank's capacity IS 45L, and it does hold that much, if almost topped-off. I ran a topped off tank past empty, and finished off with a 4.5L/100km FE for that tank. Just before the gas ran out, the FE value kept bouncing between 4.4 and 4.5. It was right on the money

 

Sorry if it seems that way. This comes up a lot and I think people are getting a little tired of explaining it over and over to people that at least initially seem pretty hostile about the whole situation.

To be fair, there are a number of related comments in the manual/quick guide:

I do agree, they should do more to make the whole variable tank size thing clear as obviously a lot of people are encountering this issue. Eco-chic, don't take it personally. You were just one of the latest in a long line of folks who have showed up telling exactly the same story. The question is how to get peoples attention and get the word out there before they run into the same problem. I think thats what Bob was trying to accomplish.

Rob

 

uhhh, but you dont have a bladder. remember.

 

Huh?

 

Good point, Pat. I was intrigued by Galaxees thread and pictures of taking apart a Prius fuel tank and bladder. The tank does look like it would hold about 12 gallons but the bladder is within the tank and would have to contain less than the metal tank itself.

http://priuschat.com/forums/prius-technical-discussion/30593-gas-bladder-exposed.html

 

It's a "leftover" from another thread:
http://priuschat.com/forums/prius-t...now-real-deal-i-ran-out-gas-4.html#post589934

MacT66: was there a purpose to that post? It seems like a continued jab of another member IMHO needlessly.:grouphug:

 

tank is so unpredictable. I drove nearly 95 miles on the flashing pip on purpose, with 2 gallons of fuel in the trunk. Pulled of quickly once i ran out. ! lol Dont try this at home please. Was when I first bought the car, now i fill up on 2 pips or 3. Sometimes i can get 11.5 g, other's only 8.5-9g...

 

This is fun!!

For anyone who thinks the fuel gauge isn't accurate because of the bladder think again.

As my friend MacT66 has pointed out to you all I have no bladder in my fuel tank so I should be blessed with a fuel gauge that is accurate enough to be fitted to the space shuttle. NASA hold off a minute please.
Here is a photo, well it is 2 photos I just took a few minutes ago, now I have cropped and pasted one picture over the other and cropped the larger picture a little but apart from that and resizing to a size that isn't too big for the page the images are right off the camera, no alteration has occurred to the parts of the image I refer to here, I swear this on my grandmothers grave.


By patsparks, shot with FE270,X815,C510 at 2008-04-04


You can see on the image that there are 7 bars on the gauge, the car is on level ground. It can therefore, because my gauge is a precision instrument, be assumed I have 7/10ths of a tank left and have used 3/10ths of a tank since my last fill. This is a 2004 model so the MFD kilometres display resets automatically on refill to 0. I have not added any fuel since last refill, I did reset the trip meter at the last refill. You can see in the picture on both the MFD and the trip meter that I have covered 494 kilometres at an average consumption of 4.3 litres per 100 kilometres therefore I have consumed 21.24 litres of fuel. As this is equal to 3/10ths of a tank as indicated by the fuel gauge which can be used for measurements in a nanotechnology lab, I have a fuel tank capacity of 70.8 litres.

Now this is a bit odd I think because according to Toyota Australia the Prius has a 45 litre tank fitted and when I look under the car it looks like the genuine Prius fuel tank. The most fuel I have ever managed to squeeze in was about 42 litres.

So go ahead and call the fuel gauge in the North American Prius the "guess gauge" and blame its inaccuracy on the bladder but the reality is the gauge is set up like this on purpose, it has nothing to do with the bladder and Toyota aren't the only manufacturer that does it.

Day before yesterday I topped up my work car, a 2006 Holden Commodore, similar to the new Pontiac G8 but with a 3.6L V6. The gauge read just over 1/2 a tank and it took 48 litres of fuel. This car has a 73 litre fuel tank but according to the absolutely accurate gauge in the Holden, remember this car hasn't got a bladder either, according to the gauge the Commodore must have at least a 96 litre tank. This even though I have only ever managed to squeeze 70 litres in for 1 fill up at the most.

Why does a manufacturer make a gauge that isn't linear in its behaviour?
Well most people know they have a full tank when they have just filled up and it really isn't critical to know exactly how much fuel is in the tank when it is full, after all your not about to run out are you? So a lot of you may have noticed you can drive over 100 miles before the gauge starts to drop, no one worries about this because your not about to run out are you? As the fuel level drops you will be more concerned about the fuel level so the segments at the low end of the gauge each represent a smaller amount of fuel than the one to its right, therefore giving a driver a better idea about how much fuel is in the tank toward the end that really matters, the empty end. We all notice that the last half of our fuel goes quicker than the first half so we fill up sooner to prevent running out.

 

I forgot to add, I am not allowed to make any comment about anything, I haven't got a bladder in my fuel tank.

Also I added the red line around the instrument picture.

 

when I really fill it up I can get 140 miles before it drops below full..BUT its bad because it floods the venting system... I just fill up when I reach 300 miles.. Am I the only one that's has to hold the nozzle all the way out to get the gas to flow freely..If I put it in the tank it clicks off every half gallon

 

The UK Prius does not have the bladder in the tank. I find I can go up to "maximum I have recorded" 173 miles on the first pip. Filling the tank without the pump continuously cutting off can only be done with the fuel filler nozzle on the pump inverted "handle uppermost".

John (Britprus)

 

I consistently get 60 miles after the pip flashes then fill up with about 10+ gallons, 2007 Prius. I assume I have a 2 gallon reserve once the flashing begins.

 

does this mean that the usa is the only country with the stupid bladder? is it because our govt sucks and the japs still hate us? if my tank ever fails I'm gonna get a Canadian tank smuggled in.