Engine Oil Grades List: Your Complete Guide to Choosing the Right Oil for Your Engine

If you’ve ever stood in an auto parts store staring at a wall of engine oils, confused by labels like “5W-30,” “SP,” or “ACEA C3,” you’re not alone. Engine oil grades are critical to your engine’s health, but decoding them feels like learning a new language. This guide breaks down the most common oil grade systems—including API, SAE, ACEA, and others—explains what each label actually means, and helps you match the right oil to your vehicle. By the end, you’ll skip the guesswork and choose oil with confidence.

Why Engine Oil Grades Matter More Than You Think

Your engine is a complex machine with moving parts that rub against each other thousands of times per minute. Oil isn’t just a lubricant—it’s a protective barrier, a coolant, a cleaner, and a sealant. Using the wrong grade can lead to accelerated wear, reduced fuel efficiency, or even catastrophic engine damage. Conversely, the right oil keeps your engine running smoothly, extends its life, and ensures it performs at its best. That’s why understanding oil grades isn’t optional—it’s essential.

The Two Primary Oil Grade Systems: API and SAE (and How They Work Together)

Oil grades are defined by two main organizations: the American Petroleum Institute (API) and the Society of Automotive Engineers (SAE). While they serve different purposes, they work hand in hand to tell you everything you need to know about an oil’s performance.

API Grades: Performance Standards for Modern Engines

API (pronounced “ay-pee-eye”) sets standards for oil performance based on how well it meets the needs of modern engines. These grades are denoted by a two-letter code (e.g., SN, SP, CJ-4) where the first letter indicates the oil’s service category (e.g., “S” for gasoline engines, “C” for diesel engines), and the second letter denotes its relative performance level (with later letters indicating newer, better standards).

Here’s a breakdown of the most common API grades for gasoline engines:

  • SN (and SN Plus/SP): Released in 2010 (SN) and updated in 2018 (SP), these are the latest standards for gasoline engines. Oils with SN/SP grades are designed to protect against low-speed pre-ignition (LSPI)—a problem common in turbocharged engines where oil droplets ignite prematurely, causing damage. They also offer better protection against sludge, varnish, and wear, even in high-temperature conditions.
  • SM: Introduced in 2004, SM oils are still used in some older vehicles but lack the LSPI protection of newer grades. They’re sufficient for engines without turbochargers or direct injection, but not ideal for modern turbo engines.
  • SL/SJ/SH/Sg: These are older standards (dating back to the 1990s and early 2000s) that lack the advanced additives and protections of SN/SP. They’re generally not recommended for vehicles made after 2010, as they may not meet manufacturer requirements for newer engines.

For diesel engines, API uses “C” grades (e.g., CJ-4, CK-4, FA-4). CK-4 is the current top standard, offering improved protection against soot, wear, and oil consumption in high-efficiency diesel engines. FA-4 is a lower-viscosity option for newer diesel engines designed to run on it.

SAE Grades: Viscosity—The “Thickness” of Oil

SAE (Society of Automotive Engineers) focuses on viscosity, which is a measure of how easily oil flows at different temperatures. Viscosity is critical because oil needs to be thin enough to flow when the engine is cold (to start quickly and lubricate moving parts immediately) but thick enough to stay put and protect engine components when the engine is hot.

SAE grades are listed as two numbers separated by a “W” (for “Winter”), e.g., 5W-30. Here’s what each number means:

  • The first number (before the W): Indicates viscosity at low temperatures (specifically -35°C/-31°F). Lower numbers mean thinner oil that flows better in cold weather. For example, 0W oil flows more easily than 10W oil when starting a frozen engine.
  • The second number (after the W): Indicates viscosity at high temperatures (100°C/212°F). Higher numbers mean thicker oil that resists thinning out under heat. A 30-weight oil is thicker at operating temperature than a 20-weight oil.

Common SAE viscosity grades include:

  • 0W-20: Ultra-low viscosity, ideal for modern fuel-efficient engines (especially those with turbochargers or direct injection) and cold climates.
  • 5W-20/5W-30: The most common grades, balancing cold-start performance with high-temperature protection. Suitable for most gasoline engines.
  • 10W-30/10W-40: Thicker oils often used in older engines, high-performance engines, or hot climates where extra protection against thinning is needed.
  • 15W-40/20W-50: Heavy-duty grades for large trucks, commercial vehicles, or engines subjected to extreme heat or heavy loads.

Not all engines can use every viscosity grade. Your vehicle’s owner’s manual will specify the recommended SAE range—for example, “5W-20 or 5W-30.” Using oil outside this range (e.g., 10W-40 in a car that calls for 0W-20) can reduce fuel efficiency, cause poor cold starts, or lead to insufficient lubrication.

Regional and Manufacturer-Specific Grades: ACEA, ILSAC, and JASO

While API and SAE are global, other organizations set additional standards tailored to regional needs or specific engine types:

ACEA (Association des Constructeurs Européens d’Automobiles): European Standards

ACEA (pronounced “a-see-uh”) focuses on European vehicles, which often have tighter emissions regulations and more advanced engine designs. ACEA grades are denoted by letters and numbers (e.g., A1/B1, C3) where the first letter(s) indicate the oil’s performance for gasoline (A) or diesel (B) engines, and the second number denotes its performance level.

Key ACEA grades include:

  • A1/B1, A3/B3, A3/B4: These are “mainstream” grades. A3/B4 is the most common, offering high protection for modern gasoline and diesel engines, including turbocharged units. A1/B1 is a lower-viscosity option for fuel-efficient engines.
  • C1-C5: “Low SAPS” (Sulfated Ash, Phosphorus, Sulfur) grades designed for engines with gasoline particulate filters (GPFs) or diesel particulate filters (DPFs). Lower SAPS means less ash, which prevents filters from clogging. C3 is a top choice for GPF-equipped engines, balancing protection with low emissions.

ILSAC (International Council on Clean Transportation): Fuel Efficiency Focus

ILSAC, a joint effort by automakers and oil companies, sets standards for oils that improve fuel efficiency. The most common ILSAC grade is GF-6, which replaced GF-5 in 2020. GF-6 oils are backward-compatible (they work in engines requiring older GF-5) but offer better protection against LSPI and improved fuel economy. Look for the “Starburst” symbol on the bottle to identify GF-6 oils.

JASO (Japanese Automobile Standards Organization): For Motorcycles and Small Engines

JASO focuses on oils for motorcycles, small engines (lawnmowers, generators), and other non-automotive applications. The most common JASO grade is MA/MA2, which ensures oils meet friction requirements for wet clutches (common in motorcycles). Using the wrong JASO grade (e.g., an automotive oil with no MA rating) can cause clutch slippage in motorcycles.

How to Choose the Right Oil Grade for Your Vehicle

Now that you understand the grading systems, here’s how to apply that knowledge:

  1. Check Your Owner’s Manual First: This is non-negotiable. Manufacturers specify the exact API, SAE, and sometimes ACEA/JASO grades required for your engine. Ignoring these recommendations can void your warranty and damage your engine.
  2. Consider Your Climate: If you live in a cold climate (frequent sub-zero temperatures), opt for lower “W” grades (e.g., 0W-20 instead of 5W-20) to ensure quick oil flow during startup. In hot climates, higher second numbers (e.g., 5W-40 instead of 5W-30) provide better high-temperature protection.
  3. Account for Driving Habits: If you frequently tow, drive in stop-and-go traffic, or own a high-performance/turbocharged engine, use the “top-tier” grade recommended by your manual (e.g., SP over SN, CK-4 over CJ-4). These oils have advanced additives to handle extreme stress.
  4. Watch for Engine Age: Older engines (pre-2010) with worn seals may benefit from conventional or high-mileage oils (labeled with “HM” or “High Mileage”), which contain seal conditioners to reduce leaks. Newer engines (2010+) require synthetic oils meeting API SP/ACEA C3 to protect turbochargers and GPFs.

Common Myths About Oil Grades (and the Truth)

  • Myth: “Thicker oil is always better.”
    Truth: Thicker oil can reduce fuel efficiency and may not flow properly in cold weather. Always follow your manual’s recommendation.
  • Myth: “I can use a higher API grade than my manual says.”
    Truth: Higher grades (e.g., SP instead of SN) are backward-compatible, but only if your manual allows it. Some older engines may not need (or could be damaged by) the additives in newer grades.
  • Myth: “All 5W-30 oils are the same.”
    Truth: No—5W-30 is a viscosity grade. Oils with the same SAE grade can have different API/ACEA ratings (e.g., SN vs. SP, A3/B4 vs. A1/B1), which affect performance.

Final Thoughts: Invest in the Right Oil—Your Engine Will Thank You

Understanding engine oil grades isn’t just about decoding labels; it’s about protecting one of the most expensive components of your vehicle. By matching the oil to your engine’s needs (using your manual as a guide) and considering climate and driving habits, you’ll ensure your engine runs reliably for years. Remember: when in doubt, ask a trusted mechanic or refer to your owner’s manual. Your engine’s longevity depends on it.

Back to blog