Motor Oil Classifications

Understanding Vehicle Motor Oil Classifications: Choosing the Right AMSOIL Synthetic

Navigating the world of motor oil can be overwhelming, but selecting the correct oil is the most critical decision for engine longevity. Modern engines are more complex, requiring advanced, high-performance lubricants. Motor oil classifications—set by organizations like the American Petroleum Institute (API), the International Lubricant Standardization Committee (ILSAC), and ACEA—are designed to help you choose the right product.

For 2026 and beyond, superior protection means choosing 100% synthetic, specifically products that exceed the latest API SP and ILSAC GF-6 specifications. AMSOIL synthetic lubricants are designed to not only meet these standards but to consistently outperform them, providing superior protection against engine wear, sludge, and heat.

The American Petroleum Institute (API) uses a two-letter system to define oil performance.

1. API Service Categories (The “S” and “C” System)

• Gasoline Engines (S-Class): The current, most advanced standard is API SP, introduced to combat Low-Speed Pre-Ignition (LSPI) in turbocharged engines, provide timing chain protection, and manage engine deposits. AMSOIL Signature Series and OE Synthetic Motor Oils meet this stringent standard.
• Diesel Engines (C-Class): For diesel, current standards include CK-4 and the fuel-efficient FA-4. AMSOIL heavy-duty synthetic diesel oils offer 4X to 6X more wear protection than required by standard tests.

2. ILSAC Standards (GF-6)

The International Lubricant Standardization Committee (ILSAC) focuses on fuel economy and engine durability, particularly for Japanese and American vehicles. The current standard is ILSAC GF-6 (subdivided into GF-6A and GF-6B). These oils are designed to improve fuel economy, provide better engine cleanliness, and enhance emission system protection. AMSOIL Synthetic Motor Oils are formulated to exceed these standards, keeping engines 81% cleaner than conventional oil.

3. Viscosity Grade (SAE)

The Society of Automotive Engineers (SAE) designates the viscosity (thickness) of oil. For example, in 5W-30, the “5W” (Winter) indicates the oil’s flow capacity in cold temperatures. A lower number means better cold-flow properties, crucial for reducing startup wear. The “30” represents the oil’s viscosity at operating temperatures. Modern synthetic oils, such as AMSOIL 0W-20, provide excellent flow in both extremes.

4. Special Manufacturer Specs (e.g., GM dexos1™)

Many manufacturers require specific approvals, such as GM’s dexos1 Gen 3 or dexosR. These specifications ensure the oil meets stringent requirements for turbocharger protection, aeration control, and engine cleanliness. AMSOIL offers several products that are certified by, or exceed, these specialized requirements.

Why Choose AMSOIL Synthetic Lubricants?

Not all synthetic oils are created equal. AMSOIL 100% Synthetic Motor Oils are engineered to go beyond industry standards:

• Superior Wear Protection: AMSOIL Signature Series provides 75% more engine protection against horsepower loss and wear.
• Maximum Cleaning Power: With up to 50% more detergents than OE oil, AMSOIL keeps engines cleaner.
• Extended Drain Intervals: AMSOIL Signature Series is guaranteed for up to 25,000 miles or one year, allowing for fewer oil changes.
• Superior Turbo Protection: AMSOIL protects turbochargers 72% better than required by the GM dexos1 Gen 2 specification.