What was found
DURING 100 HOUR INSPECTION, FOUND NO 3 EXHAUST VALVE STICKING. CLEANED GUIDE, CONTINUED IN SERVICE. 94 HOURS TIS LATER, CYL NO 4 EXHAUST VALE IS STICKING, WITH IMPACT MARK ON PISTON, INSTALLED A REPAIRED CYLINDER/SERVICEABLE PISTON. 35.7 HOURS TIS LATER, CYNLINDER NO 2 EXHAUST VALVE IS STICKING. INSTALLED A REPAIRED CYLINDER/SERVICEABLE PISTON. CLEANED NO 1 EXHAUST GUIDE. WE HAVE BEEN USING PHILLIPS XC 20W50 SINCE TAKING OWNERSHIP OF THIS AIRPLANE IN NOV 2019. PRIOR OPERATOR USED SHELL PRODUCTS. THIS SCHOOL PERATES 5 DA20C1S AND THIS IS THE FIRST INSTANCE OF VALVE STICKING WE HAVE EXPERIECED.