BBC: Senators in the United States have approved legislation requiring American car manufacturers to increase fuel efficiency by an average of around 40 per cent. The energy legislation requires car firms to achieve 35 miles per gallon (15 kilometres per litre) in fuel efficiency, up from 27.5 miles a gallon for passenger cars and 22.2 miles a gallon for mini-vans, SUVs and other light trucks. A massive boost in the use of greener fuel sources, including ethanol as motor fuel, to …