Hand Crank Grain Mill Lubricants

As my mother-in-law was cleaning out my wife's grandmother's house my mother-in-law came across an old grain mill that she thought we would like. It is a nice, sturdy, cast iron thing that has clearly seen a lot of use in its day, but everything seems to work okay. :-)

So I took it apart and cleaned it thoroughly, but as I was putting it back together it occurred to me that I don't know what lubricant to use.

Any suggestions?