Engine Oil Grades: Understanding the Different Types and Classifications

21 Aug 2024

Engine oil is the lifeblood of any vehicle. This vital fluid lubricates, cools, and protects the engine from wear and corrosion. When browsing the vast selection of motor oils on store shelves, all those numbers and letters must be clarified. What do they all mean? Read on to understand the different engine oil grades and classifications to help you select the optimal product for your vehicle.

Index

• Basics of Engine Oil Grades
• Understanding Motor Oil Classifications
• Types of Engine Oil Grades
• Common Engine Oil Types: Exploring the Options
• Motor Oil Grade Classification Systems
• Motor Oil Grades
• How to Choose the Right Engine Oil
• Conclusion
• FAQs

Basics of Engine Oil Grades

Engine oil grades denote critical viscosity and performance specifications, allowing the selection of the optimal formula to match operating conditions. Understanding the different engine oil types allows drivers and mechanics to select the optimal oil viscosity and formulation to match their vehicle's engine and operating conditions.

How to Read Engine Oil Grade?

The SAE system classifies engine oil viscosity grades like 5W-30. The first number denotes winter/cold flow grade - lower means easier pumping when cold. After the "W," the second number reflects hot operating viscosity - higher indicates thicker oil that better retains film strength under heat. This numbering conveys an oil's flow at temperature extremes.

Relevance in the Automotive Industry

Engine oil grade classifications evolved in the automotive space as multi-viscosity oils were developed to replace single-grade types. This allowed superior protection across diverse operating conditions in modern engines. Specifying oil grades by SAE viscosity ratings has become the global industry standard when defining engine oil performance criteria.

Understanding Motor Oil Classifications

The API oversees a motor oil grading system certifying performance levels for gasoline and diesel engines. "S" classifications denote petrol engine oils, while "C" ratings denote diesel oils. These letters are followed by standards indicating the performance category and year introduced, such as SN for 2021 petrol engine specifications.

SAE viscosity grades like 5W-30 were discussed earlier regarding numerical oil classifications. However, beyond dictating viscosity, SAE defines vital oil testing protocols and sequences to qualify overall engine oil quality and performance.

Types of Engine Oil Grades

Engine oils come in single-grade and multi-grade formulas, with fundamental differences in their temperature operating ranges. Multi-viscosity oils using viscosity index improvers provide the most robust protection across diverse climates.

Single-Grade vs Multi-Grade Oils

• Single-Grade Oils:

  Single-grade oils have a fixed viscosity index, meaning they do not adapt to temperature changes. They are formulated to perform at either cold winter or hot running temperatures but not effectively across a broad range.

• Multi-Grade Engine Oils:

  Multi-viscosity oils like 10W-30 and 5W-40 operate across a wider temperature band. This means they flow adequately when cold yet maintain sufficient lubrication film through viscosity index improvers at high temperatures.

Common Engine Oil Types: Exploring the Options

Engine oils are categorised based on their base oil sources and chemistry. Conventional mineral oils are refined from crude oil, offering a lower production cost and proven performance. Synthetic oils are formulated from synthetic base stocks, providing improved cold flow, high-temperature stability, and premium wear protection.

Synthetic blends combine conventional and synthetic base oils, offering the benefits of synthetics at a lower price. Finally, high-mileage oils use additives and seal conditioners specifically to protect ageing engines beyond 75,000 miles.

Motor Oil Grade Classification Systems

The SAE manages the most common engine oil classification system based on viscosity - e.g. 5W-30 grade oils.

What do the SAE Viscosity Rating Numbers Mean?

The "winter" number denotes cold-temperature viscosity. Lower values, like 0W or 5W, indicate easier oil flow for cold starting, which aids lubrication during warm-up.

The second "summer" number rates viscosity performance at high temperatures. Higher values like 40 or 50 reflect thicker oil that better resists viscosity breakdown when hot. This maintains oil film thickness. So, oil like 10W-30 flows adequately when cold yet provides enough lubrication for protection once it is at the optimum operating temperature.

Motor Oil Grades

While SAE defines many viscosity grades, several see heavy use in passenger vehicles. 0W-20 oils deliver maximum fuel economy, which many late-model gas eng. require. 0W-30 flows well when cold, which suits many Asian countries. 5W-30 handles broad temperature ranges, leading to wide usage. Synthetic 5W-40 provides stable protection across the operating range as a premium multi-grade. The older top rec. 10W-40 has proven viscosity brackets used in gasoline and diesel apps.

How to Choose the Right Engine Oil?

When selecting engine oil, keep these essential steps in mind:

• Check your owner's manual for the recommended viscosity grade and minimum performance specification.
• Ensure the oil meets current API SN or ILSAC GF-6 quality ratings.
• Choose the proper SAE viscosity based on your climate and type of driving.

Conclusion

Choosing the proper engine oil grade sustains performance and longevity. Consult your manual for the recommended viscosity and API quality rating. Quality oils like Gulf Oil's advanced formulations exceed specifications to protect modern engines. Prioritise the oil change intervals and grades advised by your manufacturer for smooth operation and durability.

FAQs