I bought Liquid Wrench lubricating oil, Slilcone spray and Lithium spray grease and I tested all of them on some styrofoam and only the lithium melted it. Should I avoid using this on painted and plastic stuf? I was going to use it on car door hinges but I don't want it to harm the paint or plastics. Why did it melt the styrpfoam and what does it mean? I'll probably just use the Silicon spray or oil on the cars. Thanks!