I have a Craftsman GT 5000 series tractor with a Kohler Pro 25 hp motor (model #CV730S) , It seams to be eating oil, There are no leaks or puddles when it sits and not running but when I run it for about and hour and check the oil the dip stick shows about half way between "add and full". I always check the oil before I start it up and have to add oil if I run it more that a half an hour. I have 104 hours on the motor and bought this tractor new about 3 years ago. The problem started about 2 months ago. I have never had to add oil before was always on full. Is there anything that I can check before I take it to my local dealer? I know it has over head valves could the problem be there?