How to Keep Car Doors From Freezing Shutby Kyle McBride
To prevent your door and window weatherstripping from freezing to your car doors, you need to eliminate moisture on the weatherstrips. Take a can of silicone spray -- available at auto parts stores -- and spray enough silicone onto a rag to wet it. Wipe the wet rag over the weatherstrips. Make sure you do the strip around the inside of the door and the strip around the inside of the door opening. Wipe enough silicone onto the weatherstrips to leave them shiny, but not necessarily wet. Also, wipe the silicone-wetted rag on the window weatherstrips and on the trunk lid weatherstrips to keep them from freezing shut.
The silicone won't hurt painted surfaces, but because it repels moisture it'll make spots that won't take wax well when you wash and wax your car the next time. By spraying the silicone into the rag before applying it to the weatherstripping, you have better control and can avoid over-spray onto the painted surfaces. Don't use a petroleum-based product such as WD-40 or petroleum jelly on the weatherstripping. While they will prevent the door from freezing closed, they will also degrade the rubber.