Brushed and vacuumed flu pipes and heat exchangers Replaced oil filter, nozzles, and strainers Checked all electrical connections and safeties Preformed combustion and smoke tests When cleaning up after the service we found a small pinhole leak on the bottom of the oil canister. Replaced the bottom half of the oil canister with a new one. Also found that the porcelain on the water heater jtube had cracked. Took pictures and measurements for replacement. Furnace-12.0%o2 42ppm co 0 smoke Water heater-8.2%o2 29ppm co 0 smoke While testing the furnace there was a spike in o2 when the blower turned on indicating a crack in the heat exchanger. The o2 went from 5.6%o2 to 12.0%. Recommended replacing furnace soon before the crack causes issues with the heat. Quoted price for porcelain repair is 110 plus tax