Chrysler Group LLC spends $20 million to acquire an assembly plant from Old Carco LLC, remnant of the defunct Chrysler LLC.

Located in Sterling Heights, MI, the affected plant is home to the Chrysler Sebring and Dodge Avenger midsize cars.

Old Carco is the holding company for assets that belonged to the auto maker before it exited bankruptcy last year.

The deal, which requires court approval, will extend the plant’s life through 2012. It had been set to close this year.

Chrysler’s product plan calls for the Sebing and Avenger to get a refresh this year. But both are slated for replacement in 2013.

The auto maker’s next-generation midsize cars will be based on a platform supplied by partner Fiat Auto SpA. Fiat has said it will be a scaled-to-size version of its C-EVO platform that shoulders the overseas-market Alfa Romeo Giulietta, launching now.

Chrysler spokeswoman Jodi Tinson says the plant sale does not guarantee Sterling Heights will be the production site of Chrysler’s next-gen midsize cars.