Can the filtered lubricating oil still be used?

Absolutely! Industrial lubricant oil can be reused in most cases after filtration, and this is a crucial and standard step in lubricant maintenance and cost control.

However, this isn't a simple "yes" or "no" decision; it depends on the condition of the lubricant, the type of contaminants, and the level of filtration technology.

The following explains in detail:

Why can filtered lubricant be reused?

Lubricant oil's primary functions are lubrication, cooling, sealing, and cleaning. During use, it is gradually degraded by contaminants, including:

1. Solid particles: such as dust, metal wear debris, and seal material debris. These are the most common contaminants that accelerate equipment wear.

2. Moisture: This comes from air condensation or cooling system leaks. It can cause oil emulsification, additive degradation, and metal corrosion.

3. Other fluids: The accidental mixing of different oils.

The purpose of filtration is to remove these contaminants, restore the cleanliness and performance of the lubricant, and extend its service life, thereby:

Saving costs: both in terms of new oil procurement and waste oil disposal.

Equipment Protection: Clean lubricating oil significantly reduces equipment wear and prevents unplanned downtime.

Environmental Protection: Reducing waste oil production aligns with sustainable development.

Key Factors Determining Reusability After Filtration:

1. Whether the Lubricant's Base Oil and Additives Have Lost Their Effects:

Oxidative Deterioration: Lubricating oil reacts with oxygen at high temperatures and under metal catalysts, generating acidic substances and sludge. If the oil is severely oxidized, turning dark or black, and has an excessively high acid value, even if solid particles are filtered out, its chemical properties have changed, resulting in reduced lubrication performance and increased corrosiveness. In this case, the oil needs to be replaced rather than simply filtered.

Additive Depletion: Antioxidant, anti-wear, and rust-inhibiting additives in lubricating oil are gradually depleted during use. Filtration cannot replenish these additives. If the additives are completely depleted, even if the oil appears clean, it will not provide adequate protection.

2. Type and Extent of Contaminants:

Filterable Contaminants: These include the solid particles and free water (unemulsified) mentioned above, which can be completely removed through methods such as microfiltration and vacuum dehydration. Difficult-to-treat contaminants: If the oil is severely emulsified (oil and water mixed into an emulsion), or if it contains other chemicals or incompatible oils, separation and treatment can be extremely difficult and may not be economically viable.

3. Filtration Technology Used:

Simple Filtration: Only removes large solid particles and has limited effectiveness.

Precision Filtration: Using high-precision filter elements (e.g., 1-3 microns) can effectively remove fine particles.

Comprehensive Treatment: Modern oil purification equipment is often integrated, including:

Coalescing and Dehydration: Effectively removes water.

Vacuum Dehydration: Deeply removes trace moisture and dissolved water.

Centrifugal Separation: Suitable for separating heavy contaminants and water.

Best Practices and Recommendations:

1. Oil Analysis:

This is the most scientific and reliable method for determining oil quality. Regular sampling and laboratory analysis can accurately determine the oil's:

Viscosity: Whether it is within the specified range.

Acidity: Determines the degree of oxidation.

Water content. Particulate contamination (such as ISO cleanliness codes).

Additive element content and wear metal content.

Based on the analysis report, the expert can clearly determine whether the oil is "recoverable" or "must be replaced."

2. ｓｅｌｅｃｔ appropriate filtration equipment: 

Based on your oil contamination, choose a filtration device or vacuum oil filter with appropriate functions (such as water removal and particle removal).

3. Establish a standardized lubricant management procedure:

Maintain lubricant cleanliness during transportation, storage, and refueling.

Regularly filter oil used in critical equipment (offline or online).

Perform regular oil analysis to track trends.

Lubricant contaminated with solid particles and water can be fully reused after proper filtration and purification.

Lubricant that has undergone severe chemical oxidation deterioration or additive depletion cannot be used even after filtration and must be replaced.

Oil analysis is the gold standard for determining whether a lubricant is "recoverable" and is highly recommended.

Therefore, when considering filtering for reuse, please do not operate blindly. It is best to conduct oil testing first or consult a professional lubricant service company.