Don a friend told me she used spare air/fix a flat on her car when her tire was flat to get it to the store. When she brought the car in to fix it, they told her she would need a new tire, because that stuff makes it impossible to patch. Have you ever heard this? I carry a can, since I'd rather be mobile than stuck in the middle of nowhere with no cell signal, but just curious if this is true, or someone took advantage of a nice lady!