All around America, you can see the failed attempts at converting to the metric system. The half-liter juice box. The smattering of highway signs listing kilometers. But the one place where metric lives on -- and needs to die -- is our cars.

The hidebound auto industry won't give it up, even on the most all-American of cars. We asked Karl Brauer, editor at large at Edmunds.com, about the liter thing. "It's purely marketing," he says.

He noted that with American muscle cars, it might make all the sense in the world to switch the message back to American standard measurements that an average guy or gal can actually understand:

"If I was the Dodge guy and they said, 'What do you want to do with Challenger?' (you) could reconfigure (the engine) to actually give it 426" cubic engines, the magic number that made the 1960s/'70s versions famous.

Brauer and Ford spokesman Richard Truett say the start of the liter measurement of engines dates to the mid-1960s Pontiac GTOs, apparently to give it more of a Euro-tinge to go with its Euro GTO ("Gran Turismo Omologato") name. The classic Pontiac 389 cu. in. V-8 became the 6.5 liter in the GTO and was proudly touted as such in big badges on the sides, just aft of the front wheels.

But, Truett says, the new Mustang wears its 5.0 liter badge with pride. "The '5.0' on the side of the 2011 Mustang GT is probably the biggest engine size badge we have ever put on a car!" he writes in an e-mail.

The auto industry was one of the first targeted to convert to metric. And it never gave it up. At least the fasteners on most cars usually aren't a mix of metric and standard anymore. Most cars now, sadly, only have metric.

So wouldn't it make sense to bring back cubic inches to measure the displacement of muscle-car engines? "Hmm. Doubt it," Truett writes. "It's so old school now."