As they do with fashion and culinary wonders, the Europeans are continuing to take the lead in tightening fuel-economy standards as well.

The European Commission (EC) has proposed fleetwide greenhouse-gas emissions standards for cars that are about 30 percent stricter by the end of the decade than they were last year. Van emissions standards would be tightened by about 20 percent, Green Car Congress reports.

Automakers would need to cut average new-car emissions to 95 grams of CO2 per kilometer by 2020, down from the 135.7-gram standard for 2011, according to the publication. Van emissions would be reduced to 147 grams per kilometer in 2020, down from 181.4 grams in 2010.

Unsurprisingly, the European Automobile Manufacturers' Association (ACEA) secretary general says it'll be tough for vehicle makers to reach these mandates by the end of the decade. But the EC says it's worth it, because, over the next two decades, consumers would cut their annual fuel costs by about $37 billion per year while oil use would decrease by 420 million tonnes, should such standards be put in place.

To put the European proposal in perspective, the 2020 mandate would be slightly stricter than the U.S. emissions standards the Obama Administration proposed last year for 2025. That proposal, which would require automakers to boost fleetwide fuel economy by about 70 percent to a real-world average of about 40 miles per gallon, is expected to be ratified later this year.