Like many relics this forklift has a milky color to the engine oil and we don't change it as often as we should. There has always been a quarter size oil spot under where it is parked after each use. Normal use is 10 minutes for us. Yesterday we had an unusual 40 minute run time and there was a 4" diameter spot. Yet the dipstick still indicates full or just above full. Without closely examining the source, it does seem to be coming from the area near the rear main bearing. Any ideas?