Performed 2 oil pms Brushed and vacuumed flue pipe and heat exchanger Replaced oil filter, nozzle, and strainer Checked all electrical connections and safeties Performed combustion and smoke tests Furnace- 7.5%o2 40 ppm co 0 smoke Water heater- 7.1%o2 3ppm co 0 smoke While performing the maintenance we found very high levels of sludge in both oil filter canisters. Would recommend getting sludge additive for the oil tank