Hi Lorna,

Mineral oil is a thin oil. probably best known is 3 in 1. 

sharpening stones work best when used wet with some kind of honing fluid. … A light oil is desirable because a heavy or viscous oil will interfere with the sharpening action of the stone. A non-hardening oil is required because an oil that hardens, as most vegetable oils do, will clog a stone reducing its efficiency.

i wouldn’t recommend a cooking oil as 3 in 1 is both easily available and far better for both the sharpening action and longevity of the stone.

Hope this helps