When close to running out of gas, most drivers know how to stretch the last gallon. This works of course because fuel efficiency depends on driving style as well as on vehicle design.
It is increasingly common for cars to come equipped with fuel economy indicators of various levels of sophistication - some cumulative, some real-time, etc. Prius and other hybrids have particularly nice dashboard displays, and many of their drivers take the implied challenge and learn how to maximize mileage.
Recently, Toyota announced plans to introduce in certain Japanese-market models an "Eco Drive Indicator", which boils fuel-efficiency down to a single on/off light, based on such factors as speed, transmission efficiency, and acceleration. The idea is to help the driver save fuel, and raise awareness of how that reduces climate-changing CO2 emissions.
Toyota states that the Eco Drive Indicator can improve fuel efficiency by approximately 4%. My own anecdotal experience with real-time fuel-economy indicators suggests that much larger savings are possible (especially if your preferred driving style is as inefficient as mine!).
Real-time feedback is a beautiful thing. As they say....out-of-sight, out-of-mind; but a dashboard eco-feedback display provides a constant reminder, and makes it easy for drivers to learn how driving style affects fuel economy.
I suspect that the single most cost-effective way to reduce oil consumption would be to mandate that every vehicle be equipped with a real-time eco-feedback display. I also suspect that this would be less-controversial than raising CAFE standards!
Indeed, we are considering a requirement that all Automotive X PRIZE entrants have such a display. Maybe there should even be a special award for the coolest one. What do you think?