Automakers can double the fuel economy of their fleets by 2050 and save the world a lot of oil and greenhouse-gas emissions, if they start right away on a "radical but achievable agenda" – and they don't need to go all-electric to do it.

That's the assessment of the Global Fuel Economy Initiative, a group of international agencies that made their appeal in a report to automakers Wednesday at the Geneva Motor Show.

The group said its initiatives could save the planet six billion barrels of oil per year by 2050 and lead to a 2-gigaton reduction in greenhouse-gas emissions, even if miles driven globally double by 2050.

Automakers won't have to switch wholesale to cars powered by electricity or hydrogen to get there, the group claimed. Just retooling vehicles to be built with lighter materials, more efficient tires and other components and better engines and drive trains could do the trick, the group said.

Still, "full hybridization of a much wider range of vehicles" to be powered partly by electricity would be a main feature of the goal of improving new cars' fuel economy by 30 percent by 2020 and by 50 percent by 2030, another of the group's goals, it said.

Now the question is, will automakers be able to take up the challenge? The ongoing economic recession is driving down auto sales and pushing some automakers to the brink of bankruptcy (see Showing Off Green Cars Amid Economic Gloom), casting some doubts on their pledges to build more fuel-efficient fleets.

While troubled American automakers General Motors and Chrysler have promised to increase their fleets' fuel economy with hybrid-electric and all-electric vehicles to come, they also have asked the federal government for two multi-billion dollar rounds of aid to avoid potential insolvency (see U.S. Automakers Get Federal Bailout).

And Toyota, which leads the hybrid car market with its Prius, has seen sales of the fuel-efficient vehicle plummet along with sales overall, and said it expects last year to bring the company its first operating loss in 70 years (see Toyota to Build All-Electric Car by 2012).

But the Global Fuel Economy Initiative said Wednesday that it sees the recession as a chance for governments to pressure automakers to adopt its fuel-efficiency measures.

"In confronting the economic recession this is a real opportunity for governments to combine support for the auto industry with measures to achieve environmental and energy policy goals," said Nobuo Tanaka, executive director of the International Energy Agency, a member of the initiative.

Other members include the United Nations Environment Program, the International Transport Forum and the F.I.A. Foundation.

The group has said it will meet with automakers in Geneva, and wants to get started right away by helping governments form national fuel economy policies through four pilot projects.

The group didn't say which countries it was targeting, but did highlight that the global car fleet is expected to triple by 2050, with four-fifths of that growth to come in developing countries.

President Barack Obama has called for the U.S. auto fleet to improve fuel efficiency by 40 percent by 2020 (see Obama: Cars Need to Improve Gas Mileage by 40%). And the European Union in December approved measures for new vehicles to reduce their greenhouse-gas emissions by 18 percent by 2015.