What lubricant most closely resembles the secretions from a woman's vagina?

Some people tell me it's like Vaseline, and some say it's baby oil.

Vaseline (the petroleum jelly, not the lotion) is too thick. Baby oil is closer – but it's not greasy like either of those oil-based substances. Actually, you know what comes out when you have a runny nose? That's almost identical to vaginal lubrication, because it's made of the same stuff (largely water and mucous).