Avoid WD-40 on your chain. Instead, go to Home Depot and get a quart of chainsaw chain oil. It's labelled "Chain, Bar, & Sprocket Oil" and comes in a plastic quart can like motor oil.

I've been using it on my recumbent chain. It's great stuff.

It's designed for chains. It costs a buck. It will provide you with a lifetime supply of oil for all your bike chains, all your family's bike chains, and all your friends' bike chains. And you won't find any oil cheaper unless you're related to King Abdallah of Saudi Arabia. In which case, you'd probably be driving around in your custom Lamborghini, not on your bike.