Gasoline Engine Oil (Petrol engines): e.g., SAE 5W-30, 10W-40 (H3-1)
Gasoline engine oils are categorized primarily by their base oil type and their performance is defined by key features and industry specifications like API and ILSAC standards. The primary function is to lubricate, cool, clean, and protect engine parts.
Types of Gasoline Engine Oil (H4)
- Conventional (Mineral) Oil: This is refined directly from crude oil and is the most basic and affordable option. It is suitable for older, less demanding engine designs but breaks down faster under high heat or extreme conditions.
- Synthetic Blend Oil: A mix of conventional and synthetic base oils with additives. It offers better performance and protection than conventional oil (especially for heavier loads or higher temperatures) at a lower cost than full synthetic oil.
- Full Synthetic Oil: Chemically engineered in a lab with a uniform molecular structure and fewer impurities, providing superior performance and protection. It is ideal for modern, high-performance, and turbocharged engines and performs better in extreme temperatures (both hot and cold).
- High-Mileage Oil: This is specifically formulated for older engines (typically over 75,000 miles/120,000 km). It often has a conventional or synthetic base but includes special additives and seal conditioners to help reduce oil consumption, prevent leaks, and minimize engine wear in older engines.
Key Features and Specifications (H4)
Key features of gasoline engine oils are related to their performance characteristics, which are measured against industry standards:
- Viscosity: This is the oil's resistance to flow and its most important property. Multi-grade oils, such as 5W-30 or 10W-40, are most common and maintain adequate flow across a wide temperature range. The "W" indicates "Winter" performance (lower numbers mean better cold flow for startup protection), and the second number indicates high-temperature viscosity (higher numbers provide a stronger film under heat).
- Lubrication and Wear Prevention: The primary function is to create a protective film between moving metal parts to reduce friction and wear, which extends engine life
- Thermal and Oxidation Stability: High-quality oils resist breaking down at high temperatures and forming sludge or deposits when exposed to oxygen, a critical feature for modern hot-running engines.
- Cleaning and Contaminant Control: Additives, such as detergents and dispersants, keep engine components clean by preventing deposits and suspending contaminants (like soot and acids from combustion) until the next oil change.
- Corrosion Protection: The oil contains additives that neutralize acids and form a barrier to protect metal parts from rust and corrosion.
- Industry Standards (API and ILSAC): These certifications ensure an oil meets minimum performance requirements set by vehicle manufacturers.
- API (American Petroleum Institute): The "S" category is for gasoline (Service) engines. The current latest standard is API SP, which is backward compatible with previous standards like SN/SN Plus. API SP specifically addresses issues like low-speed pre-ignition (LSPI) in turbocharged engines.
- ILSAC (International Lubricant Specification Advisory Committee): Oils meeting the latest standard, ILSAC GF-6 (GF-6A and GF-6B), offer improved fuel economy, better wear protection, and LSPI protection. GF-6A applies to common viscosity grades (e.g., 5W-30), while GF-6B is for very low viscosity oils like 0W-16.