Wentworth's complete fueling history
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Wonderful results, though the next fillup will reveal whether the bladder was contracted (this is not a joke...). You see, on Generation II Prii like Wentworth (model years 2004-2009) there is a gas bladder which expands and contracts with the gas volume found inside the car. It does this so that it can keep the overall volume of the tank down to prevent fuel evaporation, since those vapors can leave the tank during refueling, thus wasting gas, your money, and of course slightly harming the environment. If the bladder does not fully expand during fuel up, then you will pump fewer gallons until it's "full", and the math will give you a higher mpg than reality. It all works out over multiple tanks, of course, so no worries, it's all about the overall average.
That being said, it's possible this was my actual mileage, with almost 10% of the tank being those 37 miles at 80.9 mpg displayed, and a couple trips up in the 70s, plus a whole bunch in the mid 60 mpgs. Arguments for the gas bladder not being fully expanded, though, would be the couple trips I tried on the highway (see below), where I got mid to high 50 mpgs.
Time will tell...now for some tank pictures. (EDIT: The fill-up after this one confirmed that the 65 mpg number was real!)
Wanted to experiment with highway driving. 55.5 mpg over 26 miles. Although not bad for any car in 23°F, I'll need more practice. Hobbit is able to find a surprisingly fast sweet spot and gets 70 mpgs on the highway. You can see on mine most of the time it hanging barely over 50 mpg, just at the end since it was late and there were no cars on the road I used some nice hypermiling for last 10 minutes of 100+ mpg. One other highway trip on this tank (this route but in reverse) showed 58.5 mpg.
Thing is, I'll still try to avoid highway driving. This ride below is the same departure point and final destination as above, but is 6 miles or so shorter with mpg shown at 69.7 mpg. You can guess which route I'll take regularly...
71.7 mpg over 27 miles. Same route as the 73.3 mpg from earlier in the week.