It is a very clear cut case. In a machine which is run without any oil cleaning system, the wear and tear of components goes on increasing with time reducing the efficiency of the machine and so increasing the energy consumption.Assuming the life span of the machine at 12000 hours, the energy consumption will be something in first 3000 hours, will be more in next 3000 hours and will increase accordingly in future.
But if the oil is kept reasonably clean, almost no wear and tear, hence no reduction in the efficiency of machine and no significant increase in energy consumption. It will be approximately same during last 3000 hours as during first 3000 hours. Moreover there will be increase in the life of the machine itself.
I dont have any technical data, but it is very clear from the common sense itself. If somebody studies the effect of clean oil on some machines through out their life span, it will give solid backing to this thought.