Can I Use Engine Oil as Hydraulic Oil?

It is not the best practice to use engine oil as hydraulic oil, but in certain situations, it can be used as a temporary replacement. Nevertheless, there are significant considerations before using it:

Key Differences Between Engine Oil and Hydraulic Oil

Viscosity & Flow Properties

Hydraulic oil is specially designed for maximum flow and pressure transfer.
Engine oil possesses a different viscosity range, which is intended for lubrication and not hydraulic pressure.

Additive Composition

Anti-wear, anti-foaming, and anti-rust additives are specific in hydraulic oil designed for hydraulic applications.

Engine oil contains detergents and dispersants that help clean engine parts, but it can generate foam and contaminate a hydraulic system.

Temperature & Stability

Hydraulic oil provides steady operation under pressure conditions and varying temperatures.
Engine oil is used in high-temperature combustion conditions but might not operate effectively in hydraulic circuits.

Wear Protection & Lubrication

Hydraulic systems are dependent on accurate lubrication to avoid wear on valves and pumps.
Engine oil can sometimes fail to possess the correct lubrication characteristics in hydraulic seals and pumps.

When Can Engine Oil be Used in a Hydraulic System?

Temporary Emergency Use – In the absence of hydraulic oil, engine oil can be used as a temporary filler.
Older Machines – Older equipment (such as some models of John Deere tractors) permits multi-use oils.
Low-Pressure Applications – Engine oil can function without much problem if the hydraulic system is at low pressure.

When Should You Avoid It?

High-Pressure Systems – The lubrication will be inadequate, resulting in heavy wear.
Long-Term Use – It will cause foaming, overheating, and seal damage.
Sensitive Equipment – Precision hydraulic systems need proper viscosity and additive packaging.

Conclusion
Engine oil may be substituted for hydraulic oil only as a last choice and in low-pressure, non-critical uses. For the best performance and lifespan, use the hydraulic fluid specified by the manufacturer at all times.