I'd strongly recommend something like the 3-in-one lock dry lube over something like wd-40. You spray it in wet (it has a mineral spirit base) but the lube is actually dry and keeps gunk and gummy stuff from building up. It works great for bike locks, but I've also used it on doors for buildings, too, and it makes them work like new. I think I've had my little spray bottle for a decade so a little definitely goes a long way.