The range of powertrain options seems almost endless.

There're hybrids, plug-in hybrids and electrics. There're more fuel-efficient internal combustion engines that burn gas, diesel and biodiesel. There's natural gas and even hydrogen. And automakers need to prepare for all of them.
That, at least, is the opinion of Ford CEO Alan Mulally, who affirmed the carmaker's commitment to producing a variety of powertrains during a question-and-answer session Monday at the Fortune Magazine "Brainstorm Green" event in Laguna Niguel, Calif.

"None of us know which one is going to end up being the solution, depending on the technology department," he said. "So in the meantime, we're going to pursue all of them."

In 2012, Ford's lineup is starting to reflect that approach. The company has introduced its EcoBoost V-6 engines across its lineup, and been surprised as it outsells V-8s in its perennially popular F-150 pickup.

And the all-electric Ford Focus, which carries a 110-mile range on a single charge, debuted earlier this year.

Mulally foresaw a future in which urban residents who wouldn't suffer from "range anxiety" might be primary consumers of electric cars, while suburban drivers and others may favor hybrids or plug-in hybrids.

Over the next decade, he forecast that 60 percent of global sales would fall in the B and C class category, comprised of vehicles like the Ford Fiesta and Ford Focus.

As customers seek smaller and more fuel-efficient cars--it's the number one criteria for current shoppers, he said--it's critical that automakers make headway on improving battery efficiency and reducing battery weight.

In order to offer consumers the fullest range of powertrains, he said producing the cars on the same production line would create the necessary efficiency to make that possible.

"We can't guess what the demand is going to be, but on the same line, 70 to 80 percent of the parts are the same, so you can imagine the efficiencies and sustainability of that," Mulally said. "Then we'll make it in the quantities that they want, and just move the production up on each different vehicle."

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