Numbnuts says in post #15 that he sprays WD40 on his chain every other trip, and although I wouldn't it's up to him what he uses on his bike - it's his after all!
Done that often the light oils listed in the data sheet will certainly reach the metal on metal moving surfaces in the rollers, and at that frequency will keep them well covered. With that frequency of use it's clear why he's getting good chain life using it. I give him full marks for taking the trouble to maintain his bike that often. The cans now say there's PTFE in WD40 so I'd expect it to work better than before as a lubricant.
I'm far too lazy for that. My chains get maintenance about once a fortnight when I do several jobs on the bikes. They get the oil - wipe - oil treatment with the much heavier and more viscous oil sold for bikes. This is also enough to keep the relevant bits covered in oil. (I'm not going to get 6500 miles out of a chain, if for no better reason than that I do silly things like riding up onto the Quantocks and Blackdowns).
I've never seen any deterioration in metal WD40's been used on, and I find it one of the best cleaners for paint and metal. I use it on the bike, the car, and anything else that gets greasy dirty, as I said in my earlier post. I don't understand how or why it works on braking surfaces, but neither they nor the blocks seem to suffer any harm from its use. I don't see why it works as a mild penetrating oil for unsiezing things, but it does.
If anyone choses to use WD40 on their bike's moving parts and they do it in a way that works then good luck to them.
Judging from what I often see on bikes next to mine on stands in various places many would do well with a dose of WD40 - their transmissions haven't seen anything except salt and water for several years!
