I have aquired a case ingersoll 224 lawn tractor. This machine was given to me by my father. He bought it used about 15 years ago and rebuilt it the second season he owned it. At that time the machine had over 800 hours on it when the hourmeter failed. My question is that this tractor is driven by a hydraulic motor on the two speed transaxle and that is powered by a pump driven by the 14 horsepower K321AS kohler engine. The fluid in this system has never been changed to my understanding. Ingersoll recomends a 20W-40 motor oil in the summer and a 5W-20 motor oil in the winter. Also this system is used to lift the mower deck via a hydraulic cylinder. I was wondering if these recomended fluids would be the best canadites for the job. And I was wondering what would be a good interval to change it at. Also it does not have a filter. Thanks ahead of time for the help and information.