Engine Oil Grades Chart: The Ultimate Guide to Viscosity and Performance​

Understanding the engine oil grades chart is the single most important step you can take to ensure the longevity, efficiency, and proper operation of your vehicle's engine. This chart, composed of codes like 5W-30, 0W-20, or SN, is not random jargon but a precise, globally standardized language that tells you exactly how the oil behaves in your engine under heat and cold. Choosing the correct oil grade specified by your vehicle's manufacturer is non-negotiable for optimal protection. Using the wrong grade can lead to poor lubrication during cold starts, inadequate protection at high temperatures, reduced fuel economy, and potentially severe engine damage over time. This guide will decode every element of the oil grades chart, providing you with the knowledge to make informed decisions for your car, truck, or motorcycle.

The modern engine oil grades chart is a multi-faceted label that communicates several key performance characteristics. It primarily describes the oil's ​viscosity—its resistance to flow—and its ​performance level—the quality of its additive package and its suitability for specific engine types and emission systems. The chart integrates standards from several major global organizations.

​1. SAE Viscosity Grade: The Core of the Chart​

The most prominent feature on any bottle of motor oil is its SAE viscosity grade, such as 5W-30 or 10W-40. SAE stands for the Society of Automotive Engineers, the body that standardizes this measurement. Viscosity is often described as an oil's "thickness," but a more accurate term is its flowability. An oil must be fluid enough to flow quickly and protect engine parts at startup in freezing temperatures, yet thick enough to maintain a protective film between metal surfaces at the engine's normal operating temperature.

The SAE system uses a dual-number format for most modern oils: a "W" grade (for Winter) and a high-temperature grade.

• ​The "W" (Winter) Number:​​ This number (e.g., the "5" in 5W-30, the "0" in 0W-20) indicates the oil's flow characteristics at low temperatures. ​A lower "W" number means the oil flows more freely in the cold.​​ A 0W oil is thinner and pumps faster at sub-zero temperatures than a 5W oil, which in turn is better than a 10W oil. This ensures critical engine components receive lubrication within seconds of a cold start, minimizing wear.
• ​The High-Temperature Number:​​ This number (e.g., the "30" in 5W-30, the "40" in 10W-40) represents the oil's viscosity at the engine's normal operating temperature (approximately 100°C or 212°F). It indicates the oil's ability to maintain film strength and protect against wear under heat and shear stress. ​A higher number denotes a thicker oil film at high temperature.​​

Therefore, an oil labeled ​SAE 5W-30​ has the cold-flow properties of a 5-weight oil and the high-temperature viscosity of a 30-weight oil. This "multi-grade" capability is achieved through advanced base oils and viscosity index improvers (VIIs).

​Common SAE Viscosity Grades and Their Typical Applications:​​

• ​SAE 0W-20, 0W-16, and even 0W-8:​​ These are ultra-low viscosity oils designed for modern fuel-efficient gasoline engines. They reduce internal friction, improving gas mileage. They are almost exclusively specified for newer models from Asian and American manufacturers (e.g., Toyota, Honda, Ford, GM) from approximately 2010 onward. They require very precise engine clearances.
• ​SAE 5W-20 and 5W-30:​​ The most widespread grades for gasoline engines in the last two decades. ​5W-30​ is often considered the universal default for a vast range of vehicles in temperate climates, offering excellent all-season protection. ​5W-20​ is a common factory fill for many North American and Asian vehicles to meet Corporate Average Fuel Economy (CAFE) standards.
• ​SAE 5W-40 and 0W-40:​​ These are higher performance, often full-synthetic oils. ​5W-40​ is frequently recommended for European performance vehicles, turbocharged engines, and some diesel engines. ​0W-40​ offers superior cold-start protection (0W) combined with robust high-temperature film strength (40), making it a favorite for high-performance applications and severe climates. It is commonly found on the approved lists for BMW, Mercedes-Benz, and Audi.
• ​SAE 10W-30 and 10W-40:​​ These were the workhorse grades for older vehicles. ​10W-40​ is still commonly used in many conventional and synthetic blend oils for older engines, motorcycles, and in warmer climates where cold-start performance below -20°C is less critical.
• ​Single-Grade Oils (e.g., SAE 30, SAE 40):​​ These are now largely obsolete for modern passenger car engines. They have no multi-grade properties, meaning they are very thick in the cold and thin out significantly when hot. Their use is typically restricted to vintage cars, some small air-cooled engines (lawn mowers), and specific racing applications where the engine is operated at a constant high temperature.

​2. API Service Classification: The Quality & Performance Standard​

While the SAE grade tells you how the oil flows, the API (American Petroleum Institute) service symbol tells you how well it protects and what type of engine it's designed for. This is the "donut" symbol on the back of the bottle.

The API classification uses a simple two-letter code:

• ​The First Letter:​​ Denotes the engine type.
  • ​​"S" (Service/Spark Ignition):​​ For gasoline engines.
  • ​​"C" (Commercial/Compression Ignition):​​ For diesel engines.
• ​The Second Letter:​​ Denotes the performance level. The alphabet progresses with time; a later letter indicates a newer, more stringent standard.

​Current and Common API Classifications for Gasoline Engines (S- categories):​​

• ​API SP:​​ Introduced in 2020, this is the current highest standard. It provides improved protection against:
  • Low-speed pre-ignition (LSPI) in turbocharged direct-injection (TDI) engines.
  • Timing chain wear.
  • Deposits and oil oxidation.
  • It also improves fuel economy. API SP oils are backward compatible and can be used in most older engines requiring older specifications.
• ​API SN (2010):​​ The previous mainstream standard. It focused on improved deposit control, seal compatibility, and compatibility with ethanol-blended fuels. The "SN PLUS" sub-category added specific protection against LSPI.
• ​API SM (2004) and earlier:​​ Older standards. While oils with these ratings may still be available, they lack the protective additives needed for engines manufactured in the last 15-20 years, especially those with emissions systems, turbochargers, or direct injection.

​Current and Common API Classifications for Diesel Engines (C- categories):​​

• ​API CK-4 (2017):​​ For high-speed four-stroke diesel engines. Designed for 2017+ model year engines, it offers improved shear stability, aeration control, and protection against catalyst poisoning, oxidation, and viscosity loss due to soot.
• ​API FA-4 (2017):​​ A separate category for certain lower viscosity oils designed for on-highway, model year 2017+ diesel engines. These lower viscosity oils (like XW-30) are formulated to improve fuel economy. ​They are not backward compatible​ unless explicitly recommended by the engine manufacturer.
• ​API CJ-4 (2010):​​ The previous standard for diesel engines equipped with advanced emissions control systems like DPFs (Diesel Particulate Filters). Still suitable for many engines.

Many oils are formulated for both gasoline and light-duty diesel engines and will carry a dual rating, such as ​API SP/GF-6A CK-4.

​3. ILSAC Standard: The Fuel Economy Focus​

ILSAC (International Lubricant Standardization and Approval Committee) is a joint effort of U.S. and Japanese automobile manufacturers (AAMA and JAMA). ILSAC standards are essentially a subset of API specifications that include mandatory fuel economy performance, lower volatility, and filterability requirements.

The ILSAC "starburst" symbol is a quick visual guarantee that the oil is suitable for virtually all gasoline-powered passenger cars and light trucks. The current standard is ​GF-6, which was split into two sub-categories:

• ​GF-6A:​​ Backward compatible with previous GF standards and equivalent to API SP with fuel economy testing.
• ​GF-6B:​​ For even lower viscosity oils (like 0W-16) and is not backward compatible.

An oil that meets ​ILSAC GF-6A​ will also meet ​API SP.

​4. ACEA Sequences: The European Performance Benchmark​

For European vehicles (Volkswagen, BMW, Mercedes, Porsche, Volvo, etc.), the ACEA (European Automobile Manufacturers' Association) sequences are often as important as, or more important than, API classifications. ACEA standards are typically more stringent in specific areas like sludge protection, piston cleanliness, and soot-handling performance.

ACEA classifications use a letter-number format (e.g., A3/B4, C3):

• ​​"A" series:​​ For gasoline engines.
• ​​"B" series:​​ For light-duty diesel engines in passenger cars and vans.
• ​​"C" series:​​ ​Mid SAPS (Sulphated Ash, Phosphorus, Sulphur) oils.​​ This is a critical category. These oils are designed for vehicles with advanced after-treatment systems like Gasoline Particulate Filters (GPFs) and Diesel Particulate Filters (DPFs). The lower ash content prevents clogging these expensive components. C-category oils are now standard for most modern Euro 6/VI and later vehicles.
  • ​C2:​​ Low SAPS, mid HTHS viscosity. Focus on fuel economy and catalyst compatibility.
  • ​C3:​​ Low SAPS, high HTHS viscosity. The most common specification for many modern European performance and luxury vehicles. Offers robust protection with DPF/GPF compatibility.
  • ​C5:​​ Low SAPS, low HTHS viscosity. For the latest engines requiring ultra-low viscosity oils with DPF/GPF compatibility.
• ​​"E" series:​​ For heavy-duty diesel engines.

​5. Original Equipment Manufacturer (OEM) Approvals: The Final Authority​

Beyond these industry standards, car manufacturers issue their own rigorous approval codes. Using an oil with the correct OEM approval is the absolute safest choice. These approvals are listed in tiny print on the oil bottle's back label.

• ​Volkswagen/Audi/Seat/Skoda:​​ ​VW 508 00 / 509 00​ (for latest models, often requires specific 0W-20 oil), ​VW 504 00 / 507 00​ (long-life standard for earlier models), ​VW 502 00​ (for older performance models).
• ​Mercedes-Benz:​​ ​MB 229.71 / 229.72​ (latest low-ash), ​MB 229.5 / 229.51​ (earlier performance standards).
• ​BMW:​​ ​BMW Longlife-04, -12FE, -17FE+​​ (the "FE" variants indicate Fuel Economy).
• ​General Motors:​​ ​GM dexos1​ (gasoline, current Gen 2 specification), ​dexos2​ (for European vehicles and some diesels, low-ash).
• ​Ford:​​ ​Ford WSS-M2C947-A, B, C, etc.​, and ​Ford WSS-M2C950-A.
• ​Chrysler (Stellantis):​​ ​MS-6395.
• ​Renault/Dacia/Nissan:​​ ​RN0700, RN0710.
• ​Porsche:​​ ​Porsche A40, C30.
• ​Honda/Acura:​​ ​HTO-06​ (for turbocharged models).

​How to Use the Engine Oil Grades Chart: A Practical Guide​

1. ​Consult Your Owner's Manual First:​​ This is the most crucial step. The manufacturer's recommendations, found in the lubrication or fluids section, are definitive. It will list the required SAE viscosity grade(s) for different climates and, most importantly, the required API, ILSAC, ACEA, and OEM specifications.
2. ​Understand Your Driving Conditions:​​
   • ​Climate:​​ If you live in a region with very cold winters (consistently below -20°C / -4°F), a 0W-XX or 5W-XX oil is essential. In consistently hot climates (above 40°C / 104°F), the manufacturer may approve a slightly higher high-temperature grade (e.g., 5W-40 instead of 5W-30) for added protection.
   • ​Vehicle Age & Mileage:​​ Older, high-mileage engines with some wear may benefit from a "High Mileage" formulation. These oils typically have the same SAE and API grades but include conditioners to help rejuvenate seals and reduce oil consumption, and extra anti-wear additives.
   • ​Performance & Towing:​​ If you frequently tow heavy loads, drive a performance vehicle aggressively, or track your car, following the OEM specification for a robust high-temperature grade (like 5W-40 or 0W-40) is critical. Some manufacturers even recommend a different grade for "severe service."
3. ​Synthetic vs. Conventional:​​ Modern industry standards, especially the latest API SP, ILSAC GF-6, and ACEA C-sequences, are almost exclusively met by synthetic or semi-synthetic (blend) oils. ​Full synthetic oils​ provide superior performance in virtually all areas: wider temperature range operation, better deposit control, improved fuel economy, and longer oil change intervals (if supported by your vehicle's service system). For any vehicle made in the last 15 years, a full synthetic is highly recommended.

​Common Misconceptions and Pitfalls​

• ​​"Higher viscosity (thicker) oil is always better for protection."​​ False. Using an oil thicker than recommended can cause poor cold-start circulation, increased fuel consumption, and in some cases, even less protection because the oil doesn't flow quickly enough to critical parts.
• ​​"All 5W-30 oils are the same."​​ False. One 5W-30 may meet only the basic API SN standard, while another meets API SP, ILSAC GF-6A, ACEA C3, and has BMW/Mercedes approvals. The SAE grade only describes viscosity, not performance quality.
• ​​"I can use any oil that meets the general spec."​​ Risky. For modern European cars with DPFs/GPFs, using a non-Category C oil (e.g., an A3/B4 oil instead of C3) can lead to DPF failure costing thousands. Always match the exact OEM approval if possible.
• ​Ignoring the "W" rating in cold climates.​​ Using a 10W-40 oil in a Minnesota winter when your car calls for 5W-30 can lead to accelerated wear during every cold start.

The engine oil grades chart is your roadmap to proper engine maintenance. By learning to read its codes—the SAE viscosity grade for flow, the API/ILSAC symbols for gasoline engine quality and fuel economy, the ACEA sequences for European performance and emissions compatibility, and the critical OEM approvals—you move from guessing to knowing. This knowledge protects your investment, ensures your vehicle runs as designed, and can save you from costly repairs. The right oil is the lifeblood of your engine; the grades chart is the key to choosing it correctly. Always prioritize the specifications in your owner's manual over generic advice, and when in doubt, choose an oil that meets or exceeds the highest specification listed for your vehicle.