Performed pm on oil furnace 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 7.9%o2 0ppm co 0 smoke Upon arrival customer stated the compression fitting at the oil filter was slightly leaking oil. Took the fitting apart and inspected it. Fitting looked good still but we did see a small amount of oil residue on the oil line. Also saw a small amount of oil coming from the bleeder screw on the filter canister. Put a small amount of pipe dope on the threads to help create a better seal. Sprinkled oil absorbing powder down and watched the fitting for the remainder of the maintenance. Fitting is not leaking oil any more.