My Toro Timecutter HD 54 now has a little over 50 hours on it and I decided it was time to service the transaxles. The mower has the Hydro-Gear ZT-3100s. Yesterday, I bought 5qt of Super Tech 20W50 and 2 NAPA 400102 filters. The first time is a learning experience. It will be easier from now on. The performance is improved.