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. 7.3% o2, 24 ppm, 86.5% efficient System is operating properly. The fittings on the domestic water coil have some corrosion on them. Recommend replacing the fittings.