The API GL-5 specification, established by the American Petroleum Institute, sets a performance benchmark for gear oils used in hypoid gears, commonly found in automotive differentials. Hypoid gears operate under high pressures, sliding motions, and shock loads, making them vulnerable to wear and corrosion. To meet this classification, gear oils must pass rigorous tests simulating real-world conditions. Let’s explore these critical tests.
Key API GL-5 Tests
1. L-42 High-Speed Shock Axle Test (ASTM D7452)
• Purpose: Assesses scuffing resistance under high-speed, shock-loading conditions.
• Conditions: High-speed axle rig; sudden torque spikes; defined test cycles.
• Pass Criteria: Minimal scoring on gear teeth; wear patterns within limits.
• Significance: Ensures gear oil protects hypoid gears during high-speed, shock-load events.
2. L-37 High-Torque Test (ASTM D6121)
• Purpose: Evaluates wear and extreme pressure performance under low-speed, high-torque conditions.
• Conditions: Hypoid gear rig; heavy loads; continuous operation.
• Pass Criteria: Minimal wear and scoring; intact gear surfaces.
• Significance: Confirms oil prevents metal-to-metal contact under severe sliding and pressure.
3. L-60-1 Thermal Oxidation Stability Test (ASTM D5704)
• Purpose: Tests resistance to thickening and deposit formation at high temperatures.
• Conditions: 163°C operation; aeration; 50-hour duration.
• Pass Criteria: Viscosity and deposits within limits.
• Significance: Validates oil stability under thermal stress, ensuring long-term protection.
4. L-33 Moisture Corrosion Test (ASTM D7038)
• Purpose: Measures protection against rust when exposed to moisture.
• Conditions: 65°C with water exposure; 100-hour duration.
• Pass Criteria: No significant rust or corrosion on bearings.
• Significance: Confirms oil guards against moisture-induced damage, critical for durability.
5. FZG Step Load Test (A10/16.6R/90:120)
• Purpose: Evaluates load-carrying capacity and scuffing resistance under incremental loads.
• Conditions: Back-to-back gear rig; 90–120°C operation; increasing loads.
• Pass Criteria: Must pass load stage nine without scuffing.
• Significance: Ensures oil withstands heavy loads, meeting API GL-5 standards.
Why These Tests Matter
These tests validate that API GL-5 gear oils can:
• Resist scuffing under high-speed and shock loads (L-42).
• Prevent wear and scoring under extreme pressures (L-37).
• Maintain thermal and oxidative stability (L-60-1).
• Protect against rust in moist environments (L-33).
• Deliver superior load-carrying capacity (FZG).
Meeting API GL-5 ensures gear oils provide protection against wear, scuffing, and corrosion under severe conditions typical of hypoid gears in automotive axles.
At Valorem, we prioritise solutions that meet rigorous standards. Our expertise ensures you receive lubricants designed for the most demanding applications.