We've used Costco Travel for car rentals a few times. The first one was out of St Louis, and they saved us about $150 for a 6 day rental. Another one was here at home, and it saved us about the same on an 8 day rental. The third time will also be out of St Louis, and after some price checks all over, it looks like it is saving us well over $225 for a 13 day rental.
Motel 6 website still has "Accor" on it, near the bottom, I think. And my points are still on Choice.