India, Oct. 1 -- The government on September 29 notified a third round of fuel-efficiency rules for passenger vehicles, which tighten the permitted average fuel consumption of carmakers' fleets by around 16.7% over five years, while leaving them to choose the technologies that get them there.

Since 2017, India has used Corporate Average Fuel Economy (CAFE) norms to nudge automakers into making more fuel-efficient vehicles. The idea is that if new cars burn less fuel, they emit lower carbon dioxide. The norms are issued under the Energy Conservation Act, 2001. Cars are a target because, in the power ministry's words, "The passenger vehicle segment accounts for a substantial share of India's transport energy demand and remains an important...