General Motors has made XM Satellite Radio a standard feature on 2008 model Buick, Hummer and Saab vehicles.
The radios come with a free three-month trial.
XM also is now standard across many of the vehicles in the Saturn, Chevrolet, GMC and Pontiac lineups.
GM says Cadillac was the first automotive brand to offer XM, as a factory-installed option in 2001 and later as a standard feature. XM is available now on about 50 2008 GM vehicles.
The automaker has produced more than 6 million vehicles with XM.