Probably won't hurt them. I've used both olive oil and lemon oil. But I agree with most everyone else -- buy a new set.
At this point you really need to change your strings.
It wont wreck them, it will *** your sound up... use tongue oil on frett board or virgin olive oil. There is a product called fast fret, that is a miracle worker on string life... elixer strings have a nanoweb technology that has triple the sound life to any other brand on the market... that's all I got...
Just pluck down (no pun intended) $6 and get a new, shiny set.