Drive-unit warranty on Tesla Model S now 8 years

The Tesla Model S. (Tesla)

PALO ALTO, Calif. -- Electric car maker Tesla Motors says it has extended the drive-unit warranty for its Model S sedan to make it good for eight years and unlimited miles.

The drive-unit warranty, now matching that for the battery pack, will apply retroactively to all Model S vehicles and all owners. Tesla CEO Elon Musk said in a blog posting Friday that the move reflects the company's belief that electric motors are more reliable than gasoline engines.

He wrote that the warranty extension will have ''a moderately negative effect'' on Tesla's earnings in the short term as its reserves to cover warranties are increased.

Tesla, based in Palo Alto, Calif., is preparing for the launch of a new SUV and a massive new battery plant.