Introduction

Engine oil and hydraulic oil are two distinctly different types of lubricating fluids, each designed for specific purposes. Engine oil is used to lubricate and protect the internal parts of an engine, whereas hydraulic oil is used in systems to transmit power and provide lubrication. When these two oils are mixed, the resulting mixture can have a variety of properties depending on the type and amount of oil used.

Initial Mixture Behavior

When engine oil and hydraulic oil are mixed, the mixture can exhibit different properties. Generally, engine oil has a lighter viscosity and is designed for thin films of lubrication, while hydraulic oil is thicker and is designed for more robust applications. If left to sit undisturbed for three months, the two types of oil can begin to separate. The heavier hydraulic oil will sink to the bottom, and the lighter engine oil will float on top. This separation can lead to improper lubrication of both the engine and hydraulic systems, potentially causing damage over time.

Chemical Breakdown and Contamination

Over the three-month period, the mixture is also likely to break down, especially if it is exposed to heat or moisture. This process can reduce the effectiveness of the oil as a lubricant, leading to increased wear and tear on the engine and hydraulic systems. Additionally, if the mixture is exposed to air, it can become contaminated with dust and other particles. This contamination further reduces the oil's effectiveness and can cause additional damage.

Compatibility and Miscibility

While it is true that these oils can be mixed, they are not perfectly compatible in all scenarios. Normal engine oils and hydraulic oils are mostly miscible, meaning they will not separate immediately upon mixing. However, the hydraulic oil can reduce the viscosity and chemically react with the engine oil. Important components in hydraulic oil, such as antioxidants, antiwear additives, and rust inhibitors, may not be needed in engine oil, and vice versa. Therefore, the mixture is not optimized for either application.

Conclusion

After three months, you will have a mixture of hydraulic oil and engine oil. While the oils are miscible, there is little chance of a severe reaction. However, the mixture should not be used as a substitute for either type of oil. If you find yourself needing to mix these oils, it is best to consult with a professional to ensure that the mixture is safe and effective for your specific application.

Additional Tips

Always store separate oils in their respective containers and avoid mixing them. If mixing is absolutely necessary, test the mixture for compatibility and effectiveness before using it in any critical systems.