Performed a heating pm on an oil boiler. Brushed and vacuumed. Replaced the oil filter, nozzle and strainer. Started and checked the safeties. Performed a combustion test. 4.8% o2, 32 ppm, 84.6% efficient System is operating properly. Replaced (4) circulator gaskets that have been leaking and (1) hivent that had corrosion on it. Filled the system and purged.