The purpose of the research presented in this article was to determine the impact of the storage period of engine and transmission oils on their operational properties. The prolonged storage of oils leads to a series of physicochemical changes that can significantly affect their lubrication efficiency. Changes such as reduced viscosity, changes in density, and deterioration in lubricity can lead to increased wear of the engine, transmission, and other mechanical components. The study included samples of new and five-year-old engine and transmission oils, as well as engine oil after the break-in period (with a mileage of approximately 800 km). The SAE 10W40 oil after use in an internal combustion engine shows a significant reduction in scuffing resistance (approximately one-third lower scuffing load compared to new and old oil). Long-term five-year storage also slightly reduces its scuffing resistance at higher temperatures. In contrast, long-term storage of SAE 30 oil significantly decreases its scuffing resistance across both tested temperature ranges (by about 20%). Storage time did not significantly alter the viscosity index of SAE 10W40, whereas old SAE 30 oil showed a slightly better index than new oil.