I just bought a new Sears Craftsman lawn tractor, 48 inch cut, DYT 4000 series, with a Kohler Pro, V-Twin, 25hp motor. I plan on keeping this mower for a long time. I will only use it for 30 to 40 hrs. of mowing each yr. I'm in NW Tn. and the temperature range when I'm mowing will be in the 70 to 95 degree range with the avg. mowing temp. being around 90. What would be the very best oil to use for this motor? I think it has a 2 qt. capacity. The filter that came on the motor is a spin-on Kohler Full Flow #52 50 02. Is there a better filter than Kohler, and if so, what would the brand and "crossover" reference # be? How long should I run the factory oil before changing it? Any help to my lengthy list of questions will be appreciated.