Can Hydraulic Oil Be Used as Engine Oil?

[DiGabriela]

Hydraulic oil cannot be used as engine oil. Engine oil is designed for the lubrication system of an engine, primarily for cooling and lubrication to prevent overheating of automotive components. In contrast, hydraulic oil is mainly used in hydraulic systems for torque transmission, converting torque into force applied to driven workpieces. Their functions differ significantly, making them non-interchangeable. Engine oil, also known as motor oil or engine lubricant, is a substance enhanced with additives in base oil, primarily containing anti-wear additives, detergents, dispersants, and multi-grade viscosity index improvers. The main functions of engine oil are to reduce friction and wear on moving parts and to remove sludge (one of the functions of dispersants) and varnish (function of detergents) from the engine.

[OReid]

I work in auto repair and know many people think hydraulic oil and engine oil are both for lubrication, but they can't be mixed. Hydraulic oil is mainly used in steering systems or lifting equipment, designed for pressure transfer, while engine oil specifically protects internal engine friction parts with added anti-wear agents and cleaning formulas. Using hydraulic oil as engine oil leads to insufficient lubrication due to mismatched viscosity, causing rapid engine wear or even overheating failure—costing far more than buying proper engine oil. I've seen several cars needing major repairs from this, costing thousands. Remember: always check the manual or consult experts when selecting oil to avoid false economy. Safe driving is what really matters.