No, Toyota isn't trying to con you into buying a "water powered car". They are simply trying to illustrate a simple point about fuel-efficient driving that, sadly, too few people seem to know: If you drive smoothly and try to avoid abrupt acceleration and deceleration as much as possible, you'll save fuel. It's sound advice (of course, use your judgement and don't put saving fuel above driving safely and sanely), and a good way to get a "feel" for that kind of driving is to imagine that there's a glass of water on your dash (or use Toyota's virtual water glass iPhone app) or an egg between the gas pedal and your foot (sorry, no app for that). Even better if you have a fuel economy gauge that shows you real time consumption. This doesn't mean you should drive slowly in traffic, but when appropriate, you can save a lot of gas (and CO2) by being a smooth operator.
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