You can use just about ant lightweight oil- Gun oil, 3in1, even vegetable oil. My personal favorites are CRC Screwloose or Liquid Wrench. These are both water-thin and make excellent honing oils. One note- do Not use WD-40. It's great for guns because it drys like varnish creating a barrier between the steel and any water/moisture. When used on a sharpening stone however, after the WD drys and hardens it locks the metal filings into the pores of the stone, making cleaning them a nightmare!
Ron