I have had nothing but good luck with wd40 and padlocks that live outside locking the fence year round. When I was a kid, we used it to clean our derailers and chains on our bike. Once cleaned we always followed up with a light oiling. My fence padlock has been in use 18years now, and about every three to five years it gets a little stiff, so it gets a squirt of wd40 which always does the trick to loosen it up for another 3-5 years. I agree that it is good to always oil after cleaning with WD40, I just never have on the pad lock. For lists of other uses for WD40 one of the best is graffiti removal. Some punk kid taged out neighborhood about 5 years ago. I read try using WD40, it took the paint rigth off the garbage can, must of depressed the tagger as the neighbors caught on, and by the next gargage day, we were tag free, he never came back!
Along the same lines as wd40, Ballistol used in ww2 for cleaning guns, also was sprayed on cuts and scratches to prevent infection. Pretty cool stuff