The Nihon Keizai Shimbunreports that Japan will implement regulations requiring automakers to improve the fuel efficiency of their vehicles by about 20% by 2015.
The government is considering demanding 20-25% reductions over fiscal 2004 levels by fiscal 2015. As a result, the mileage of cars that are currently required to travel 15km on a liter of gas [6.67 l/100 km or 35.3 mpg US] would have to be upgraded to more than 18km per liter [5.56 l/100km or 42.3 mpg US]. The tougher standards would apply to vehicles that are sold in fiscal 2015. Currently owned autos would not be subject to the new rules.
As much as I despise regulation, if Japan(or anyone else) is going to go that route, I think they would be much better served to go all out and require 80 mpg outright starting in the 2008 model year and an EV mandate.
Imagine if Japanese cars had a major reduction in drag coefficient, say, from ~.30 to .16, and had used things like CVTs, diesel-electric powertrains, composite bodies, ect. They could literaly not give up any performance, utility, comfort, or size and add only $2,000-5,000 to the cost of the cars.