Engine valves could use titanium alloys instead of stainless steel to achieve a reduction in weight. However, they need to be more resistant to wear. To address this difficulty, researchers have devised various surface modification methods. Thermal oxidation (TO) of Ti-6Al-4V at 600 °C for 60 h resulted in the formation of a surface rutile, TiO2, layer with a hardened oxygen diffusion zone. The TO treatment increased the surface hardness of the Ti-6Al-4V alloy from 290 ± 2 HV0.025 to 890 ± 10 HV0.025. We conducted a laboratory-scale impact-sliding wear test to compare the performance of untreated Ti-6Al-4V and TO-Ti-6Al-4V against SAE 52100-grade bearing steel balls. Before testing, we set the maximum spring and pneumatic cylinder loads at 40 N and 240 N, respectively, and ran 4297 loading cycles to simulate engine valve operation on TO-Ti-6Al-4V. Thermal oxidation reduced wear rate at the worn track's impact and sliding zones, reducing plastic deformation.