Performance Grades of Lubricant Oil define how effectively a lubricant performs under specific operating conditions beyond viscosity alone. While viscosity grades describe oil thickness, performance grades evaluate protection capability, cleanliness, durability, fuel economy, and compatibility with modern engines and machinery.
Performance grading ensures that lubricants meet the demands of advanced engine designs, emission regulations, extended drain intervals, and high-load operating environments.
International Performance Classification Bodies
American Petroleum Institute (API)
ACEA – European Automobile Manufacturers’ Association
SAE – Performance-related testing standards
OEM Specifications – Manufacturer-specific approvals
Major Performance Grading Systems
1. API Performance Grades (Global Standard)
API “S” Series – Petrol Engines
API SA – Obsolete, no additives
API SJ / SL – Older gasoline engines
API SM / SN – Improved oxidation and wear control
API SP – Latest standard with LSPI protection, turbo compatibility, and timing-chain wear control
API “C” Series – Diesel Engines
API CA – Obsolete
API CF – Older diesel engines
API CI-4 / CJ-4 – Heavy-duty diesel engines
API CK-4 – Modern EGR-equipped diesel engines
API FA-4 – Fuel-efficient low-HTHS diesel engines
2. ACEA Performance Grades (European Standard)
A/B – Passenger cars (petrol & light diesel)
C – Low SAPS oils for catalytic converters & DPF systems
E – Heavy-duty commercial diesel engines
Example ACEA Grades:
ACEA A3/B4 – High-performance passenger vehicles
ACEA C3 – Low SAPS, DPF-compatible oils
ACEA E7 / E9 – Heavy-duty commercial vehicles
3. SAE Performance Considerations
High-temperature / High-shear (HTHS) stability
Shear resistance
Foaming and air-release behavior
Key Characteristics of Performance-Graded Lubricant Oils
Viscosity Stability: Maintains oil film under variable temperatures and speeds.
Oxidation & Thermal Resistance: Prevents sludge, varnish, and acid formation.
Wear & Corrosion Protection: Anti-wear additives protect metal surfaces.
Detergency & Cleanliness: Keeps pistons, rings, and oil passages clean.
Emission System Compatibility: Low SAPS oils protect DPF and catalysts.
Refining & Formulation Properties
Base Oil Refining:
Solvent refined oils – basic performance
Hydrocracked oils – improved stability
Synthetic oils (PAO / Esters) – superior performance
Additive Technology:
Detergents (acid neutralization)
Dispersants (soot control)
Anti-wear agents (ZDDP)
Antioxidants
Friction modifiers
Volatility Control:
Low evaporation losses
Reduced oil consumption
Improved emission control
Typical Performance Test Parameters
| Parameter | Importance |
|---|---|
| HTHS Viscosity | Film strength under high load |
| Noack Volatility | Oil evaporation control |
| Total Base Number (TBN) | Acid neutralization |
| Oxidation Stability | Oil life and durability |
| Piston Cleanliness | Engine efficiency |
| Timing Chain Wear | Modern engine protection |
Applications Based on Performance Grades
Automotive & Transportation:
Passenger cars (petrol & diesel)
Commercial trucks and buses
BS-VI / Euro-VI vehicles
Industrial & Heavy Equipment:
Construction machinery
Mining and earthmoving equipment
Power generation engines
Marine & Off-Highway:
Marine diesel engines
Agricultural machinery
Locomotives
Importance of Correct Performance Grade Selection
Ensures engine reliability and longevity
Improves fuel efficiency and power output
Protects emission control systems
Reduces maintenance and downtime
Maintains OEM warranty compliance
Incorrect performance grading may lead to:
Premature engine wear
Sludge and oil degradation
Increased fuel consumption
Emission system failure