You'll earn a full 5% with every credit card purchase, redeemable toward the purchase or lease of an eligible, new vehicle from Chevrolet, Buick, Pontiac, GMC, HUMMER and Cadillac with the GM Card.

I think this is the trick that the company wants you to boost their car sales.

好像5%时攒起来买GM的车的，我们有过一张类似，从来没有用过。

Yup, and I think it's good only if you wanna buy a new car, from GM.