Ebay Motors says its listings of parts has increased dramatically in the last year, with inventory reaching about 13.9 million parts. That's more than double last year's bin, which stood at 6 million.

“It's a very fast-growing industry,” eBay Motors director Famous Rhodes said. “It's a viable channel.”

For eBay and other Web sites and classified listings, intakes, exhausts and other relatively simple do-it-yourself enhancements are the most common parts for sale.

“The tough times, consumers want to do things themselves,” Rhodes said.

In that vein, the eBay Motors has added a feature that allows users to narrow their searches for parts that could work on their cars. For example, a search on Monday afternoon for air intakes and fuel-delivery parts found 743,103 listings. But when specifying you're looking for a 2006 Dodge Charger, the search narrows to 609 listings. Plus, when you click on the part listing there are more compatability descriptions.

Additionally, the proliferation of parts on some listings is helped by the launch of modern muscle cars such as the Chevrolet Camaro and Ford Mustang, as enthusiasts search for ways to customize their rides in their own style while trolling for cheaper prices.

“The Camaro is definitely the latest blockbuster,” said Nicolas Franchet, senior director of U.S. vehicles for eBay Motors.