I don’t know, the Toyota numbers dropped by the same percentage as the pontiac numbers, and less than the Hummer numbers (as a percentage).
The next Prius numbers match what I get in real-world driving. I’m currently sitting at 460 miles driven on my last tank of gas, and expect to put about 10 gallons into the car.
I average 49 mpg overrall in my Prius. This tank has 181 miles on it, with a 52.5 mpg average. This was highway driving today, with A/C on, but low. The car has 85,000 miles on it, and hasn’t given me a single problem.