My spindle bearings were losing about 2-3 drops per hour of usage evidenced by drips down the side of the headstock, For the last week, there has been no oil loss, no leakage down the headstock and no drop in resevoir levels. The wicks are soaked and there is a film of oil on the bearing and it runs freely and is not getting warm at all. I am using 10w non detergent oil. What rate of oil loss is normal for these?