Diesel Engine Oil (Commercial/Heavy-duty): e.g., SAE 15W-40, 20W-50 (H3-2)
Commercial and heavy-duty diesel engine oils are classified primarily by their base oil type, viscosity grade, and performance specifications (e.g., API standards). Key features are engineered to handle the high temperatures, pressures, and soot production inherent in diesel engines.
Types of Diesel Engine Oil (H4)
- Conventional (Mineral) Oil: Derived from refined crude oil. It provides basic lubrication but has a shorter lifespan and less resistance to extreme temperatures compared to synthetics.
- Synthetic Blend Oil: A mix of conventional and synthetic base stocks. It offers an improved balance of performance and value, with better high-temperature stability and wear protection than conventional oil.
- Full Synthetic Oil: Chemically engineered with high-quality synthetic base oils and advanced additives. It offers superior performance, extended drain intervals, better cold-weather flow, and enhanced protection against wear and deposits.
Key Features: (H4)
- Viscosity Stability: They maintain an appropriate thickness across a wide range of operating temperatures (e.g., SAE 15W-40, 10W-30, 5W-40). The "W" indicates cold-weather performance (e.g., 15W flows better at low temperatures than 20W), while the second number (e.g., 40) denotes high-temperature viscosity.
- Detergents & Dispersants: These are present in higher amounts than in passenger car oils to prevent sludge and deposit buildup, and to suspend soot and other contaminants, transporting them to the oil filter.
- Anti-wear agents: These create a protective film on metal surfaces to reduce friction and extend component life under high pressure.
- Antioxidants & Corrosion Inhibitors: They prevent oil breakdown from heat and exposure to oxygen and neutralize acids generated during combustion, protecting engine components from rust.
- Performance Specifications (API): Current oil must meet or exceed specific performance standards set by organizations like the American Petroleum Institute (API) or the European Automobile Manufacturers' Association (ACEA).
- Extended Drain Intervals: Due to their robust formulations, these oils can support longer service intervals, reduce maintenance downtime and costs when use with an oil analysis program.
- Compatibility with Emission Systems: Modern diesel oils are "low-SAPS" (sulfated ash, phosphorus, and sulfur) to protect sensitive exhaust after-treatment systems like diesel particulate filters (DPFs) and selective catalytic reduction (SCR) units.