I have white smoke coming out of my exhuast when I start my car. I've heard that blue devil sealent will repair this problem and it will not occur again. I was wondering if anyone has used this product and did it work.

White smoke is from coolant being burned. You likely have a leaking head gasket and possibly warped aluminum head, due to the engine overheating. Hopefully, the valves are not damaged.

No sealent will take care of this problem.