snip
4. LUBRICATES: WD-40's lubricating ingredients are widely dispersed
and tenaciously held to all moving parts.
snip
Whether it is the best lubricant/cleaner/protector/penetrator is
certainly open to discussion. [I like it best for displacing water,
myself- but I have used it for all of the above from time to time]
*What* you intend to lubricate, and the atmosphere around it will
determine if WD40 is a good choice.

WD-40 has such a low film strength that it is useless for any
application that creates moderate pressures.