What happens to engine oil as it ages and collects contaminants?

As engine oil ages and accumulates contaminants, one of the primary effects is a loss of its lubricating properties. Over time, oxidation occurs in the oil, leading to the formation of sludge and varnish. These by-products can enhance friction between engine components rather than reducing it, causing wear and tear on the engine. The oil's ability to provide a protective barrier diminishes, which can compromise its function in reducing friction and heat. Therefore, the correct answer indicates that the oil becomes less effective in lubricating the engine as it deteriorates, which is a critical aspect of engine maintenance and longevity. Regular oil changes are essential to ensure that the engine operates smoothly and efficiently.