On really sloppy days, I spray the underside of the downtube, BB and chainstays with Pam cooking spray. I give the underside of the fenders a good spritz, too, helps keep them from icing up and rubbing on the tire. It's just vegetable oil so it's biodegradable, unlike WD40. Won't displace water at all, but the schmutz just wipes right off. Especially handy if you keep your bike locked up outside.