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 8.0%o2 1ppm co 0 smoke While performing the maintenance we found high levels of sludge at the oil filter and strainer. Recommend getting a sludge additive to help clear up any sludge in the oil tank. Also saw some minor corrosion starting to form on the oil line. The lime in the concrete is starting to make the underground oil line porous. Would recommend replacing the oil line in the future.