> WD-40 isn't a lubricant
WD-40 is a lubricant. The WD-40 company says it is [1], the Wikipedia article says it is, attempts to reverse-engineer the (secret) formula have found compounds typically used as lubricants and it is rather obvious to anyone who has used it.
It is the best lubricant for you application? Probably not, and that includes fans. It is probably not the best at anything unless you have an Atlas missile lying around. It is not the best lubricant, penetrating oil, water displacer, rust protector, etc... but it does all of it to some extent, and it is cheap and convenient.
Anyways, thank you for the suggestion of using gear oil, I didn't try this one and it sounds like a good candidate. I don't have marine grease but what I understand is that it is similar to basic lithium grease but formulated to resist the harsh marine environment (so maybe with some corrosion inhibitors).
[1] https://www.wd40.com/how-to/faqs/