Kohler on Grasshopper 225V,2018, we bought this mower used at an estate sale about a year ago with less than 700 hours and were told it had just been serviced! I put about 200 hours on it and decided to change oil and filter, used all Kohler parts machine ran great for about 4 hours, yesterday took it down to barn and on way bay starting knocking and then seized! I used Kohler synthetic could it be that owner used regular oil and this caused failure? Any ideas? Thanx in advance Charlie W