2011 Nissan March
2011 Nissan Micra / March – Click above for high-res image gallery

Japanese automakers will most likely need to boost their fleetwide fuel economy by 24.1 percent by 2020 to meet stringent standards being drawn up by the government, reports the Nikkei business daily.

This isn't like the recent CAFE increase in the U.S. The tentative regulations, which could take effect in spring of 2012 and measure total improvement from 2009's baseline fuel economy ratings, will apply to an automaker's entire lineup of vehicles, no exclusions, says the Nikkei. For gasoline-powered vehicles, the fuel economy benchmark will reportedly rise from an average of 16.3 kilometers per liter (38.3 miles per gallon U.S.) in 2009 to 20.3 km/l (47.7 mpg U.S.) in 2020. Some reports says that automakers who don't meet these goals will have to pay a million-yen fine ($13,070 U.S. at today's exchange rates), but how this would exactly work was not explained.

Japan's Ministry of Economy, Trade and Industry, in conjunction with the nation's Transport Ministry, will open up the fuel economy proposals for public comment before issuing final standards.