100 hours on my Scag Liberty Z with FR600V Kawasaki 18 HP. Had since new for three years now. I change the oil once a season. Using straight 40W SN from Tractor Supply now. The manual says 40W can be used in our Florida summertime 95+ degree heat. I changed the hyrdro oil and filters last season, well before the recommended interval, using Castrol 20W-50, and I can tell the difference in how it drives so I will change it every other year from now on.