Final answer:
Using WD-40 as engine oil can cause increased friction, overheating, and severe engine damage or failure due to its inability to handle high temperatures and pressures like regular engine oil.
Step-by-step explanation:
Using WD-40 as engine oil is highly inadvisable as WD-40 is not formulated to serve as a high-pressure lubricant like engine oil. Instead, it is primarily used for cleaning, displacing moisture, and lubricating non-engine components. When an engine runs, especially with the accelerator pressed in neutral for a prolonged time, it requires proper lubrication to protect the engine parts from friction, heat, and wear. Engine oil is designed to withstand high temperatures and pressures, which WD-40 is not equipped to handle. If used as a substitute, WD-40 would likely break down quickly, leading to increased friction, overheating, and ultimately causing severe engine damage or engine failure.