There isn't anything slicker than an oil lubricated bicycle and at one time many a bike was designed to use oil and not grease as their lubricant... I have several 50's bicycles that are full oilers in that the hubs and bb are all oiled and not greased.
My '55 Raleigh Lenton and '48 Rudge are as smooth a bike I have ever owned.
Using oil does have some pluses and minuses as one has to be very meticulous in keeping their bikes oiled and failure to do so can cause serious problems. Another plus is that the oil that escapes flushes out any contaminants and will keep the bearings / races clean as clean can be.
In the winter an oiled bb can run much smoother especially if a synthetic oil is used... without an oil port one needs to top up via the seat post.