Unless you are planning on welding and doing your bodywork, (plastic filler, polyester putty, molding welds, etc...) right away,.......it's a great idea to prime the frame to keep moisture away from it. (yes, it will rust)
And primer takes nothing to sand off when work is needed, so that's not an issue.
Also, soaking the frame, or any other bare metal, with any type of oil
is a horrible idea. It soaks into the surface and is a bodyman and painter's worse nightmare. Contaminants like that are bad for adhesion of anything applied to the surface, and can completely ruin a paint job later on down the line.
And before anyone says,......"well my frame and sheet metal came right from the manufacturer covered in oil
"........of course it did,.....they didn't want it to arrive to you covered in rust,.....(see, told you it would rust
) They are not concerned about the problems later on.
Remove it, and prime it,.....don't add to it.