Fill with 20W-50 motor oil (Bad Boy Hydrostatic oil is recommended) through the hydraulic fluid reservoirs until it just appears at the bottom of each transaxle's top port (approximately 2 quarts per transaxle, 4 quarts total).. These purge procedures should be imple-mented any time a hydrostatic system has been opened to facilitate maintenance or any additional oil has been added to the system. Air creates ineficiency because its compres-sion and expansion rate is higher than that of the oil approved for use in hydrostatic drive systems.
CHANGE HYDRO OIL FILTERS BY UNSCREWING THEM FROM THE FILTER HEAD. FILL NEW FILTERS WITH 20W50 MOTOR OIL BEFORE INSTALLING. USE ONLY BAD BOY REPLACEMENT FILTERS. USING ANY OTHER FILTER WILL RESULT IN DAMAGE TO THE HYDRO SYSTEM AND VOID THE WARRANTY.. I have a 2021 Bad Boy Rogue. I just performed the 50 hour initial hydrostatic system fluid & filter change. Followed the instructions in the service.