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Can engine oils replace hydraulic oils?

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To cut costs, many enterprises are keen to purchase a single multipurpose lubricant to service their vehicles and equipment whenever possible. From discounted purchases when buying in bulk to simplifying inventory and ordering, the potential benefits are clear to see. However, while in some cases this may be possible, like the use of universal tractor oils (UTOs) in the farming industry, when it comes to other types of equipment, it is a practice best avoided.

Many enterprises and operators are curious as to whether they can swap out the use of a hydraulic oil with standard engine oil. The short answer is no, users should not use engine oil to replace hydraulic, as these are two very different kinds of lubricants – each designed for a specific role and possessing different chemical compositions.

While these lubricants may appear similar, engine and hydraulic oil are not products that are interchangeable. Engine oil and hydraulic oil are made using different additive packages and base oils. This means that they will not deliver the same benefits as each other and, if used in the incorrect application, can have a negative impact. For example, using engine oil in hydraulic systems can result in poor performance and excessive wear, while using hydraulic oils to serve an engine can damage seals among other engine components.

In this blog, we’ll take an in-depth look at these two lubricants and explore why they do not represent suitable substitutes. Read on to keep your knowledge current.

Defining engine oil

An engine oil is typically described as a petroleum-based lubricant that operators use to lubricate an engine’s moving parts. It is designed to help keep the engine cool and clean and to prevent corrosion. As a rule, engine oil has a far lower viscosity compared to hydraulic oil. This means that it flows easier when performing its role at cooler temperatures.

Defining hydraulic oil

A hydraulic oil, in comparison, is a mineral oil-based lubricant that is employed to ensure hydraulic systems stay cool and run smoothly. They are specially engineered for their role and can withstand extreme temperatures and pressures. Additionally, they also have exceptional anti-wear properties.

Are engine oil and hydraulic oil the same type of products?

While both oils are lubricants, engine oil and hydraulic oil are two entirely different products. Engine oil is a built-for-purpose lubricant utilised to clean and protect internal combustion engines, while hydraulic oils are non-flammable fluids employed in hydraulic systems. While both oils may have similar jobs to perform, they cannot be used interchangeably.

Can you mix engine oil and hydraulic oil to create a blended lubricant?

If you mix engine and hydraulic oils, the resulting fluid will never perform as well as a pure hydraulic or engine oil. The most likely outcome is a mixture that has reduced viscosity and is unable to effectively lubricate moving machine parts. Furthermore, the mixed lubricant will likely lead to sludge deposit formation, which can clog up key components like filters and result in damaged engines and systems.

Why are engine oils incorrect for hydraulic systems?

Hydraulic oils are specifically designed using a natural base oil and specific additives that can cope with the severe temperatures, pressures and wear involved in processes. Formulated without these characteristics, an engine oil will break down far faster and will quickly become ineffective. This will lead to damage to the hydraulic system, leading to expensive repairs or, in worst-case scenarios, the replacement of equipment entirely and the loss of a company’s investment.

What makes hydraulic oil unsuitable for engines?

Modern hydraulic oils are not formulated to work effectively as an engine oil as they do not have the appropriate properties to lubricate and protect engine components. They also possess a lower flash point, which means that they are likelier to ignite, leading to engine damage, accidents and injuries.

Hydraulic oils are designed specifically for use in hydraulic systems. Here, they provide a high level of defence against excessive wear and tear, while engine oil is engineered to protect and lubricate components from set pressures and temperatures found within an engine.

Furthermore, hydraulic oil must never be used in a diesel tank. In such an application, the hydraulic oil will not offer effective lubrication and can quickly result in engine damage. Additionally, hydraulic oil is incompatible with diesel fuel. This means it will separate from the engine fuel and end up floating on top of it instead. This can cause damage to the injectors and loss of power.

To sum up, engine oil and hydraulic oil are two different types of lubricant and should never be substituted with one another. Equipment and vehicle operators should always consult the original equipment manufacturer’s (OEM) recommendation to achieve the best performance possible from machinery and avoid unnecessary harm to its innerworkings.


At Oil-Store, we stock hydraulic and engine oil from a variety of top brands, including Fuchs, Petronas, Q8 and Shell. Shop the range today.

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