Washington - XM Satellite Radio has partnered with General Motors on a trial program for used GM, Cadillac and Hummer vehicles, offering three months of free XM service to buyers of certified used models equipped with XM radios. The companies said XM will be available in more than 115,000 of these certified GM vehicles in 2007, and grow to more than 168,000 vehicles in 2008.

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http://www.xmradio.com/whatisxm/inyourvehicle/used-vehicles.xmc