Abstract: The lubricating performance and anti-scuffing properties of two 40BN cylinder oils were evaluated using a reciprocating friction and wear tester under simulated conditions of engine boundary lubrication and adhesive wear. Tests were conducted to measure the friction coefficient, wear loss, and anti-scuffing time. The results indicated that cylinder oil 1 exhibited a lower friction coefficient, less wear loss, and a longer anti-scuffing time, demonstrating superior friction reduction and wear resistance compared to cylinder oil 2.Analyses employing optical microscopy, ultra-high resolution scanning electron microscopy combined with focused ion beam-time-of-flight secondary ion mass spectrometry, and X-ray photoelectron spectroscopy revealed that the wear scar surface lubricated with cylinder oil 1 retained clearer honing marks and exhibited less severe wear. A boundary lubrication film, approximately 340 nm thick and composed of phosphates, sulfates, metal oxides, and carbonates, formed on the friction surface. This film is responsible for the excellent friction reduction and anti-wear performance of cylinder oil 1.

Key words: cylinder oil, friction reduction and anti-wear performance, anti-scuffing resistance performance, cylinder liner, piston ring