I started working on my older bike today. Unfortunantly it sits outside a lot because I have it up at college and have no where to put it because I use it on campus. My problem was that my rear derailer wasn't shifting at all and I found out that my cable had rusted and was sticking in the cable housing closest to the derailer. My question is what do you use to oil the cables. I just used Wd-40 because it was the only thing that I had around. It worked and the bike now shifts better then it did when it was new, but I'm sure that WD-40 is not the best thing to use. And also how often should I do this especially so this doesn't happen to my good bike that I use for riding trails.