Some else has already asked this, I suspect, but I could not easily find the answer after doing a search. Kind of a pain in cooler temperatures, as I cannot get that much gas in the tank.

 

The bladder is there to reduce gas fumes from escaping. Lots of people have trouble filling the tank fully, even in warmer climates. Some people try to 'burp' the bladder, while others wait a few moments for the bladder to 'stretch out' and then start pumping again. Both methods have their dangers in that a 'burp' may cause gas to come out, while pumping after the auto shut off valve kicks in is always dangerous.

 

The new 2010 Prius no longer has a bladder. It appears that
Toyota got the message.

Obviously the bladder was not a good idea or an improvement. Hence
its absence for 2010.

Alster

 

The removal of the bladder alone might get me to trade in my '04. Any word yet on whether the '10 will have Bluetooth hooked into the audio without having to buy the Nav?

 

According to the press release, the 2010 Nav package includes bluetooth, but that seems to be it.

 

The intent of the bladder was to almost eliminate air in the fuel tank. The air would quickly contain fuel vapours which would have to be removed by the carbon canister as the air was forced out when you pumped in fuel. The bladder made the car easier to certify at the low emission level it has (I can never remember the letter sequence - PHEV or something).

It causes some difficulty when refueling in winter, but I haven't had any problems, and I live where there IS winter!

Some think aircraft use bladders for the same reason, but that isn't the case. In aircraft the wings usually contain the fuel, and it is expensive (weight wise) to have to put a hard fuel tank inside the wing. So they used bladders. This also made drawing the fuel out of the tank easier, as the vehicle could assume many different attitudes, making fuel pickup difficult.

 

I have to say, the crazy gas tank bladder is almost a reason not to own the car. I like to fill the car at about a quarter tanks. Judging from the amount of gas I am getting, it seems like my gas tank at times shrinks to not much more than 8 gallons. Happily, warmer weather has arrived.