Performed a heating pm on an oil boiler. Brushed and vacuumed. Replaced the oil filter, nozzle and strainer. Started and checked the safeties. Blew out the oil line. The tank valve on the left tank was blocked. The oil filter was very dirty. Recommend adding an additive to help clean the oil. Performed a combustion test. System is operating properly. The was a lot of corrosion on the bad of the boiler from a previous leak. Recommend replacing the boiler due to age. The flue pipe metal is getting thin. Recommend replacing the flue pipe.