My Prius
[gas tank bladder]

Thanks for your web page decribing your thought on the Prius. I have just bought my own and filled the tank for the first time. I only put 7.14 gallons into it after going 306 miles.

Seeing your data, I had a thought: does that soft bladder stretch over time allowing more gas?

First, I subtracted out the after E miles on your chart, (this shows a distinctly increasing trend in the range of the car). However, this could just be indicative of the break-in period yielding a higher mpg over time, so I then divided out the caluclated mpg to get the number of gallons from full to E. This yeilded a fairly flat line, averaging about 8.2 gallons. So the answer is no. The amount of gas going in didn't change over time.

Hm, as in, does the gas tank mechanism have a break-in period? Gee, I don't know. I kind of doubt it because I'm guessing that the bladder is within a hard shell/container. The bladder can't stretch beyond that container, thereby letting more gas in. That's all a guess, though, because I've not gotten my hot grubby hands on a Prius service manual.

Note that gas (the liquid) does expand as a function of temperature. You just got your Prius (congratulations!), and I suspect that wherever you are in the world, it was warmer during your first tankful than it was when I first got my Prius! (January. A cold January.)

I have just bought my own and filled the tank for the first time. I only put 7.14 gallons into it after going 306 miles.

I suspect you and I did the same thing: Fill the tank the first time soon after getting the "E" signal. Sure 'nuff, the tank takes only about 7 gallons. Hey, wait, didn't I read that this was a ~12 gallon tank? Yeah, but the "reserve" tank is holding about 3 gallons!

I just turned 4,000 miles (the car did; I've turned a bit more). I'll be taking the car to the dealer for that first oil change. I'll ask 'em about the bladder. (The car's bladder.)