What are the signs of bad engine oil?

The main symptoms of oil degradation include a significant increase in engine noise, delayed power response, and an abnormal rise in fuel consumption, which are caused by increased friction between metal components due to reduced lubricating performance. Contaminated oil may cause pressure fluctuations due to viscosity changes, manifested by the oil warning light (red or yellow) illuminating on the dashboard. At this point, the vehicle should be stopped immediately for inspection to avoid severe engine damage. Abnormal exhaust emissions, such as blue-grey smoke accompanied by a pungent odor, indicate that oil is entering the combustion process and requires urgent maintenance. It is recommended that car owners check the oil condition using the dipstick monthly, monitoring changes in colour, texture, and oil level, while also evaluating engine operating sounds and performance. Using genuine oil that meets the manufacturer's specifications and adhering to regular replacement intervals can extend the engine's service life. If any of the above symptoms are observed, promptly visit an authorised service centre for professional diagnostics and maintenance.