I lean towards oil too. The open wicks make me wonder if grease cups might be missing? At least some sort of cover? You have to hunt down a service manual or compare with an identical White motor before you decide. Oil can be used on most motors, but be very careful with just one drop, maybe a second one until you can feel it has had any effect. It depens upon how much the wicks hold onto. I just had to mention it, an oil spill can be damaging. The motors I know take oil have some type wadding or wicks, and a tiny hole for applying oil. Their not nearly as large as on yours. I oldest motor I have taking oil is 1955, all pre 1950 has grease wicks.