What are the potential consequences of running an engine without oil?

Running an engine without oil can lead to severe wear and ultimately engine failure due to the critical role that oil plays in engine operation. Engine oil lubricates the moving parts, reduces friction, helps to dissipate heat, and captures contaminants. Without adequate lubrication, the metal components of the engine can grind against each other, leading to excessive wear. This can manifest as scoring on the cylinder walls, the degradation of bearings, and accelerated degradation of other essential parts. Over time, this increased friction and heat can culminate in catastrophic engine failure, such as a seized engine or the destruction of critical components.

The other options do not accurately reflect the effects of running an engine without oil. Improved fuel efficiency and increased horsepower would generally be the result of proper engine tuning and functioning, not the absence of oil. Clay buildup in the engine is not a direct consequence of lack of oil; rather, it may arise from sludge accumulation due to dirty oil or additives breaking down but not from running lean or dry in terms of lubricant.