I purchased this mower new in 2001 (I think. It has a Kolher 18 H.P. pressurized oil system. This engine still performs great. I do keep a good yearly maintenance program on the engine.
The only major problem I had after 7 years of mowing one acre, sometimes twice a week, was the rear end. It began slipping and in short time quit pulling at all. Out of desperation I pulled it out and flushed it out with kerosene three or four times then replaced with 90 wt. gear oil and a little bit of oil stabilizer then put it through the purging process nearly 30 times. Still going.