This might help a little, but the problem isn't that GM doesn't have market share. The problem is that the whole market shrank. Your strategy would be a good way to steal some market share from companies that don't offer long warranties or reliable cars. Chrysler did this with some success with the Lifetime Powertrain Warranty. While this would improve GM sales a little, it wouldn't boost the entire market. When the market gets better, however, this would be a winning solution.
