I should have asked this before, but I remember a lot of complaints or so about the fuel bladder in the tank for the Gen II. Did they get rid of it in the C (and also the Gen III of the regular Prius)? If so, what has replaced it?
As usual, I find my answers here at PriusChat! Like the OP back in 2013, I'd read about the fuel bladder, especially in the excellent "What every newb should know" sticky thread in the Newbies forum, so I've been careful at the gas pump in the couple of months I've been driving this car. Also, I was remembering the owner's manual saying "don't top up the tank." I re-read that part of the manual this morning, and noted that its stated reason is to prevent overfill and spillage. I am very glad to know that there is no bladder to worry about.
The reason not to overfill is it can damage the vapor recovery part of the pollution control system. That is true for most any car these days.
By having the gas tank stay the size of the gas in the tank, there was no room for fumes and so vapor recovery was excellent. Fuel did not slosh as it was always the size of the tank. The bladder was excellent except the user interface: Slow filling, involving bizarre rituals. (I still open my gas cap before paying, and it is 5 years since I had a Gen 2) Different sized tank by outside temperature made predicting when to refill involve prayer. The gas gauge had no more idea how much gas was left than you did. Range anxiety.
The bladder was a one-time thing on the Gen 2. All Prii after that do not have the bladder. They use a vapour canister or a pressurized fuel tank. Like Jimbo said, it was for emissions. The Prius' primary goal was to reduce emissions and fuel economy was a side benefit. The rubber bladder in the Gen 2 reduced evaporative emissions to help it earn the AT-PZEV rating (Advanced Technology-Partial Zero Emissions Vehicle) that is one step up from SULEV (Super Ultra Low Emissions Vehicle). Evaporative emissions is the gasoline vapours that form in the gas tank when you have less than a full tank. (On older cars, sometimes you hear a whoosh or a hiss when you open the gas cap to refuel - that's gasoline vapours escaping)
