Shell Rotella T 15w40. - 2004 yr. Scag Tiger Cub Mower, 48 in, kawasaki 19 hp air cooled., 1200 hrs...no leaks, no oil burning, runs like new.. governor re-set from rated 3600 rpm to 3400 rpm, oil changed annually ( approx.90 hrs ).. valves re-set and Hydrostatic drive oil changed at 800 hrs..
From past personal experience on a variety of family farm owned gas and diesel engines, with accumulated hours, DO NOT switch from dyno oil to synthetic oil., you will have leaks, seeps, drips, . Trust me..it happened.. it's not worth it... I give this mower no slack... cutting road sides, RR right of ways, tall grass, yards, etc. running wide open throttle at full load, for hours on a hot summer 90 deg. day. The secret to me is, preventive maintenance, and clean oil....