Performed a heating pm on (2) oil furnaces. Brushed and vacuumed. Replaced the nozzles and strainers. The oil filter was replaced last week. Started and checked the safeties. Performed a combustion test. 1st fl-7.7o2, 0ppm, 0 smoke, 83.7% efficient 2nd fl-10.4o2, 0ppm, 0smoke, 83% efficient System is operating properly.