I have a new to me John Deere Z445 zero turn mower. I would like to do some basic maintenance on it before the mowing season. I plan to change the engine oil and filter, air filter, fuel filter, spark plugs, and transaxle hydraulic fluid. Fluid spec: John Deere Low Viscosity HY-GARDÂ® (J20D) My question is: following the manufacturer's procedure, will I have to be concerned with any air getting into the hydraulic system? Will I have to purge the system? 1. Park machine safely on a level surface. 2. Raise operator's seat, and clean area around reservoir cap. Remove cap. 3. Clean area around hydraulic oil filter. 4. Place drain pan with at least a 9.9 L (10.5 qt) capacity under hydraulic oil filter, turn filter counterclockwise to remove and allow oil to drain completely. 5. Apply a film of clean oil on gasket of new filter. 6. Install filter. Turn filter clockwise until gasket makes contact with the mounting surface. Tighten 1/2 to 3/4 turn after gasket contact. NOTE: Reservoir capacity is approximately 8.5 L (9 qt). Total system capacity with filter is approximately 9.9 L (10.5 qt). 7. Fill oil reservoir with approximately 8.5 L (9 qt) of oil. 8. Install reservoir cap. 9. Start engine. 10. Move throttle lever to the 3/4 fast idle position. 11. Unlock park brake. 12. Run engine in full forward position for five minutes and then cycle motion control levers forward and rearward several times. Check for leaks around filter. 13. Stop the engine. Check oil level in reservoir. Add oil as necessary.