Yes, you can use WD40 on a bike chain. We can state three applications of this product, thereby justifying the statement. WD40 is often used as a chain degreaser, but they are considered harsh as compared to dawn dish soap and simple green. In that case, you can coat a bicycle lube after using WD40. It is also used as a primary solvent that strips away any existing lubricant and leaves the chain and drivetrain dry. Also, you can use WD40 3-in-1 oil as a lubricant. It provides adequate friction and protection against wear. It is up to you how and when you are going to use WD40.