What type of wear does engine oil primarily protect against in a four-stroke engine?

Engine oil primarily protects against friction wear in a four-stroke engine. This type of wear occurs when metal surfaces move against each other, creating friction that can lead to overheating and significant material loss over time. The primary function of engine oil is to create a lubricating film between these moving parts, thereby reducing the friction generated during operation.

By minimizing contact between surfaces, engine oil not only decreases wear but also facilitates smoother engine operation and contributes to heat dissipation. This lubrication is essential for maintaining the longevity and efficiency of engine components, ensuring they can withstand the mechanical forces at play without suffering from excessive wear. Other types of wear, like corrosion, fatigue, and impact, are also important concerns for engine longevity, but friction wear is the most directly addressed by the lubrication provided by engine oil.