HJ,
I don't think there is any objective data to support either grease being better for the hinge pin or a good oil. I'm betting motor oil on the hinge pin would provide more than adequate lubrication if a drop were placed there occasionally.

Most people would use grease on the hinge because it stays put. That's the purpose of what my granpa used to call 'thick ol'. In fact, greases have a lube oil and thickeners to make them stay in place.