What is the difference between machine oil and SAE automotive oil?

Machine oil is a general term for lubricants used in various machinery to reduce friction and wear, often formulated for specific applications and environments. SAE automotive oil, on the other hand, is a standardized oil specifically designed for automotive engines, classified by the Society of Automotive Engineers (SAE) based on its viscosity (e.g., SAE 30, SAE 10W-40). While machine oil can be used in numerous mechanical applications, SAE automotive oil meets specific performance criteria and specifications required for engine operation and protection.