Interestingly, WD40 is a lubricant. I used to think that since it was a penetrating oil/water sealant it wasn't a lubricant, but that's not actually the case. They even have a "myth" that discusses the idea floating out there that WD40 isn't a lubricant.

http://wd40.com/about-us/myths-legends-fun-facts/

I think it's just not very good lubricant. It wears off pretty quickly if you use it to lubricate your bicycle.

It's terrible to use it on bike chains.

It will provide some lubrication for a while, true. But it will also dissolve any of the proper lube that is there, so when the WD40 is chopped up by the chain you'll be left with nothing.

I like the Shimano PTFE dry lube[1] but there are plenty of other brands.

[1]http://www.chainreactioncycles.com/au/en/shimano-dry-lube/rp...