Why would you install side censor lights under the car to rust out.Big dollar amount to fix. Why shouldn't Chevy cover this cost????

Hello, Sorry to hear about that. The biggest contributor, as I'm sure you know, is the salt used on the roadways. Highly corrosive to paint and metal. The best thing you can do with or without repairing the issue is to keep the vehicle clean in the winter. Washing the undercarriage regularly and storing indoors will help prevent further issues. If you have any other rust buildup already, that rust will continue to accelerate unless it is remediated. Buick is to Chevrolet as Lincoln is to Ford. You have the same engineering with either brand, and the same company backing both brands (GM). Buick is a more luxurious vehicle, and the amenities may be more to your wife's liking.