Originally Posted by
facial
I have used this lubricant for many years now and I believe that, contrary to his assertions, it actually makes a chain last longer than if it is left out to rust without any oil at all.
That's not much of an endorsement. Bacon fat is better than using no oil at all.
WD-40 DOES contain a light lube in a carrier that is pretty much kerosine. However, it's not a durable or high film strength lube and has to be applied very often to have any real benefit. I know riders who use it successfully and get good chain life but they apply it every ride or two.
However, the purpose-made bike chain lubes aren't a scam to separate riders from their money. They work better and make the chain last longer with fewer applications than WD-40 will ever do. My personal favorite is ProLink but there are a lot of other good ones. Your riding conditions will have a big influence on what works best for you.