Cleaned serviced oil boiler. Replaced strainer and nozzle. Existing spin on filter is still in good shape. Brushed and vacuumed heat exchanger and exhaust pipe. Reconnected and sealed exhaust pipe. Checked expansion tank, relief valve, air vent, pressure and temp, all zones working properly. Performed combustion reading and placed results on service tag. Also flushed customers water heater, filled up 1 and a half 5 gallon buckets. System running normally.