The world's biggest gas-guzzling nation has limits after all.
After seven decades of mostly uninterrupted growth, US gasoline demand is at the start of a long-term decline. By 2030, Americans will burn at least 20 per cent less gasoline than today, experts say, even as millions of more cars clog the roads.
America's thirst for gasoline is shrinking as cars and trucks become more fuel-efficient, the government mandates use of more ethanol and people drive less.
"A combination of demographic change and policy change means the heady days of gasoline growing in the US are over," says Daniel Yergin, chairman of IHS Cambridge Energy Research Associates and author of a Pulitzer Prize-winning history of the oil industry.
The decline is expected to accelerate for several reasons.
n Starting with the 2012 model year, cars will have to hit a higher fuel economy target for the first time since 1990. Each carmaker's fleet must average 12.8 km per litre, up from 11.7 kpl. By the 2016 model year, that number must rise to 15 kpl. And, starting next year, SUVs and minivans, once classified as trucks, will count toward passenger vehicle targets.
nThe auto industry is introducing cars that run partially or entirely on electricity.
n By 2022, the country's fuel mix must include 36 billion gallons of ethanol and other biofuels, up from 14 billion gallons in 2011. Put another way, biofuels will account for roughly one of every four gallons sold at the pump.
n Gasoline prices are forecast to stay high as developing economies in Asia and the Middle East use more oil.
There are demographic factors at work, too.
Baby boomers will drive less as they age. The surge of women entering the work force and commuting in recent decades has levelled off. And the era of Americans commuting ever farther distances appears to be over.