This will sound outlandish, but any veteran driver of a Prius, or at least one who's worked hard to get decent mileage out of the hybrid, will tell you it's not. Toyota wants you to drive with a glass of water on your dash; it'll improve your MPG.
Actually, Toyota wants you to drive as though
you had a glass of water on your dash. The company has even launched a site called "A
Glass of Water."
Those who have driven a Prius, and gotten good at the "video game" display in the center dash display, which is designed to help you maximize your MPG, will realize the truth in this. It's the gentle, steady acceleration that keeps a glass of water balanced on your dash that is most efficient for your gas mileage.
For those who have an iPhone, Toyota has provided an iPhone app
that records your driving distance, time, fuel consumption and "virtual water spilled." The app shows you (on a map) where you can improve your driving habits. The results are automatically uploaded to Toyota's A Glass of Water website and compared with the results of others.
Toyota says that those who really stick to the program can gain up to 10 percent on their MPG. As with anything, however, "your mileage may vary."