API vs. SAE: What Do These Oil Codes Really Mean?

When you look at a bottle of motor oil, you’ll notice codes like "SAE 5W-30" and "API SP." But what do these labels actually mean? Understanding the difference between API (American Petroleum Institute) and SAE (Society of Automotive Engineers) ratings is crucial for choosing the right oil for your engine.

In this guide, we’ll break down:

--What SAE viscosity grades mean (e.g., 5W-30, 10W-40)

--How API service classifications work (e.g., SN, SP, CK-4)

--Why these ratings matter for your engine’s performance

--How to pick the right oil based on your vehicle's needs

1. SAE Viscosity Grades: The "Thickness" of Your Oil

The SAE rating (e.g., 5W-30, 0W-20, 10W-40) indicates the oil’s viscosity—how easily it flows at different temperatures

First number (e.g., "5W") = Winter performance (lower = better cold starts)

Second number (e.g., "30") = High-temperature viscosity (higher = thicker at operating temps)

Common SAE Grades & Their Uses:

SAE Grade Best For

0W-20 Modern fuel-efficient engines (Honda, Toyota)

5W-30 Most gasoline engines (balanced performance)

10W-40 Older engines or high-mileage vehicles

15W-50 High-performance & turbocharged engines

Key Takeaway: Thinner oils (like 0W-20) flow better in cold weather, while thicker oils (like 10W-40) protect better under heavy loads.

2. API Service Classifications: Oil Performance Standards

The API rating (e.g., SP, SN, CK-4) defines the oil’s quality and compatibility with different engines.

API Ratings for Gasoline Engines (Starts with "S")

API SP (2020+) – Best for modern turbocharged engines (better wear protection)

API SN (2010-2020) – Good for most gasoline cars (improved sludge control)

API SM (2004-2010) – Older vehicles (less advanced additives)

API Ratings for Diesel Engines (Starts with "C")

API CK-4 (2017+) – Heavy-duty diesel trucks (better oxidation stability)

API CJ-4 (2006-2016) – Older diesel engines (lower ash content)

Key Takeaway: Always check your owner's manual—using the wrong API oil can void your warranty or damage your engine.

3. How to Choose the Right Oil for Your Car

--Check your owner’s manual (manufacturers specify SAE & API requirements)

--Match climate conditions (colder regions need lower "W" numbers like 0W-20)

--Consider engine age (older engines may need high-mileage oils)

--Look for synthetic blends (better protection than conventional oils)

Why API & SAE Ratings Matter

Understanding SAE viscosity and API service classifications ensures you pick the best oil for your engine’s needs. Whether you drive a fuel-efficient hybrid or a heavy-duty truck, the right oil improves performance, fuel economy, and engine longevity

At Conlysen, we provide high-performance lubricants that meet the latest API SP & CK-4 standards, ensuring your engine gets optimal protection. Choose the right oil—choose Conlysen for reliability and innovation.