Why Air Compressor Oil Requires Excellent Oxidation Stability

Understanding Air Compressor Oil Types, Properties, and Maintenance Standards

Air compressor oil plays a critical role in ensuring the reliability, performance, and safety of air compressors across various industrial environments. Its function goes far beyond simple lubrication—it’s essential for cooling, sealing, anti-wear protection, and rust prevention. One of the most vital characteristics of high-quality compressor oil is its oxidation stability, which directly affects compressor longevity and safety.

This guide explains the classifications of air compressor oil, its performance criteria, and why oxidation stability is crucial. It also outlines oil selection, international standards, and change-out indicators—helping you make informed decisions for efficient and safe air compressor operation.

Air compressor oil is generally categorized based on the compressor structure and base oil type:

By Compressor Structure:

• Reciprocating Compressor Oil: Includes light (L-DAA), medium (L-DAB), and heavy load (L-DAC) types.
• Rotary Compressor Oil: Includes light (L-DAG), medium (L-DAH), and heavy load (L-DAJ) types.

By Base Oil Type:

• Mineral Oil-Based
• Synthetic Oil-Based

Synthetic oils like polyalphaolefins (PAO), esters, and polyglycols offer superior performance in extreme conditions.

Air compressor oil is responsible for:

• Lubricating moving components
• Cooling the system
• Sealing gaps
• Preventing rust and corrosion

Given the high-pressure and high-temperature operating conditions, ideal compressor oil must exhibit:

• High oxidation stability
• Low carbon residue formation
• Proper viscosity and temperature-viscosity behavior
• Excellent demulsibility (oil-water separation)
• Anti-rust and anti-corrosion properties

During operation, compressor oil frequently contacts high-temperature, high-pressure air and metallic surfaces, accelerating oxidation reactions. This leads to the formation of organic acids, varnish, sludge, and carbon residues, reducing efficiency and increasing wear. In severe cases, it may even trigger cylinder explosions.

To prevent such hazards, compressor oil must maintain strong oxidation resistance.

Common Test Methods:

• GB/T12709: Lubricant aging characteristics
• GB/T12581: Turbine oil oxidation stability

Two major factors contributing to compressor oil explosions include:

1. Oil sludge and carbon deposits from poor antioxidant and thermal stability
2. Decomposition of oil into light hydrocarbons and carbon dust

Prevention Measures:

• Use deeply refined, low-residue base oils
• Avoid oils containing ash-forming additives
• Choose oils with low Conradson carbon residue

Baldor compressor oils are suitable for use with:

• Air
• Hydrocarbon gases: natural gas, LPG, ethylene, etc.
• Inert gases: hydrogen, nitrogen, CO₂, CO, helium
• Reactive gases: chlorine, hydrogen chloride, sulfur dioxide

To maintain optimal performance, compressor oil should be sampled and analyzed regularly. Replace oil if any of the following occur:

• Color darkens beyond four shades
• Acid value exceeds 0.5 mgKOH/g
• Viscosity changes more than ±15%
• Pentane-insoluble matter exceeds 0.5%

Refer to standard SH/T0538-93 for change indicators in light-load rotary air compressors.

Oil selection depends on compressor type, load, and ambient conditions:

Application	Recommended Oil Type
Air-cooled piston compressor <20kW	L-DAA / L-DAB / L-DAC (32, 46, 100)
Water-cooled piston compressor	L-DAA (68, 100)
Oil-drip rotary compressor	L-DAB / L-DAC (100, 150, 220)
Oil-injected rotary screw compressor	L-DAG / L-DAH / L-DAJ (32)

China:

• GB12691-90: Reciprocating compressor oils (L-DAA, L-DAB)
• GB5904-86: Rotary oils (L-DAG)
• Enterprise standards: For L-DAH oils

International:

• DIN51506 (Germany)
• ISO/DP6521.3

Additionally, ISO/DP6743/3 classifies gas compressor oils into five types, such as DGA (mineral-based) and KGC (synthetic fluids), for various industrial gases.

Selecting the right air compressor oil is essential for maximizing compressor lifespan, energy efficiency, and safety. Oils with excellent oxidation stability help prevent harmful deposits, overheating, and catastrophic failure. At Baldor, we offer a wide range of compressor oils and solutions that meet stringent international standards and deliver superior protection in all conditions.