Streetbikes? I wouldn't. Dirtbikes are another story. Before we hit the trails we used to spray WD40 on all the plastics on our dirtbikes and quads. It made hosing them down at the end of the day a helluva lot easier.Is it safe to apply wd40 to the fenders and tank and leave it on? I would like to use it like a protectant and to shine up the bike.