Viscosity 101: How to Pick the Perfect Engine Oil for Your Car

When it comes to maintaining your vehicle’s engine, choosing the right engine oil is crucial. One key aspect of engine oil that many consumers overlook is its viscosity. Understanding viscosity and its implications can help you make informed decisions, ensuring your engine runs smoothly and efficiently. In this blog post, we will delve into viscosity ratings, how viscosity affects engine performance, and how to choose the right viscosity for your vehicle. We will also highlight some popular engine oil viscosities available in South Africa.

Explanation of Viscosity Ratings

Viscosity is a measure of a fluid’s resistance to flow. In the context of engine oils, it indicates how easily the oil pours at a specific temperature. Viscosity ratings are typically represented by a combination of numbers and a letter, such as 5W-40. This rating is part of the SAE (Society of Automotive Engineers) classification system.

  • The “W” Rating: The number preceding the “W” (which stands for winter) represents the oil’s viscosity at cold temperatures. Lower numbers mean the oil is thinner and flows more easily in cold weather, which is essential for starting the engine in cold conditions.
  • The Second Number: The number following the “W” represents the oil’s viscosity at high operating temperatures. Higher numbers indicate a thicker oil that can withstand higher temperatures without breaking down.

For example, a 5W-40 oil performs well in a wide range of temperatures, providing good flow at cold temperatures and maintaining its viscosity at higher temperatures, making it suitable for various driving conditions.

How Viscosity Affects Engine Performance

The viscosity of engine oil plays a significant role in engine performance and longevity. Here’s how it impacts different aspects of your vehicle’s engine:

  • Cold Starts: During cold starts, the oil needs to flow quickly to lubricate the engine components. A lower viscosity oil (like 5W-30) ensures that the oil circulates rapidly, reducing wear and tear during startup.
  • High Temperatures: At high operating temperatures, the oil must remain thick enough to provide a protective film between moving parts. An oil with higher viscosity at these temperatures (like 20W-50) ensures that the engine components are adequately lubricated, preventing metal-to-metal contact and reducing engine wear.
  • Fuel Efficiency: Thinner oils (lower viscosity) generally reduce friction, which can improve fuel efficiency. However, if the oil is too thin, it might not provide sufficient lubrication, leading to increased wear.
  • Engine Protection: The right viscosity oil creates a balance between being thin enough to circulate quickly at startup and thick enough to protect the engine at high temperatures. This balance is essential for optimal engine protection and performance.

How to Choose the Right Viscosity for Your Vehicle

Selecting the correct viscosity for your engine oil depends on several factors, including your vehicle’s make and model, driving conditions, and climate. Here are some guidelines to help you choose the right viscosity:

  • Manufacturer’s Recommendations: Always start by checking your vehicle’s owner’s manual for the manufacturer’s recommended oil viscosity. This recommendation is based on extensive testing and is tailored to your specific engine.
  • Climate Considerations: In colder climates, you may need an oil with a lower winter viscosity (such as 5W-30) to ensure easy starts and proper lubrication. In hotter climates, a higher viscosity oil (like 20W-50) may be more appropriate to maintain performance and protection at higher temperatures.
  • Driving Conditions: Consider your typical driving conditions. If you often drive in stop-and-go traffic or tow heavy loads, you might need an oil with higher viscosity to handle the increased engine stress.

Popular Engine Oil Viscosities in South Africa

South Africa’s diverse climate and driving conditions mean that a range of viscosities are popular among consumers. Here are some common options:

  • 10W-40: A versatile option suitable for many vehicles, offering good performance in a variety of temperatures. For example, the Sasol Synthetic Engine Oil 10W-40 is a popular choice.
  • 5W-30: Ideal for colder regions or vehicles that require a lower viscosity oil for better fuel efficiency. The Sasol Synthetic Engine Oil 5W-30 is widely used.
  • 20W-50: Suited for older vehicles or those operating in hotter climates. Oils like Sasol Multigrade Engine Oil 20W-50 provide excellent protection at higher temperatures.
  • 5W-40: A good all-rounder for modern engines requiring high performance across a range of temperatures. The Sasol Synthetic Engine Oil 5W-40 is a reliable option.

Understanding viscosity and its impact on engine performance is essential for choosing the right engine oil. By following your vehicle manufacturer’s recommendations and considering your local climate and driving conditions, you can select an oil that ensures optimal engine protection and efficiency. With a wide variety of high-quality engine oils available in South Africa, if you’re ready to give your car the healthier option, don’t settle for anything less than the best. As an approved Sasol Techno Oil™ Distributor, Enterprise Lubricants offers a wide range of engine oils and other lubricants. Explore and shop our full range at

Remember, the right viscosity matters – it’s the key to a healthy engine and a smooth ride.

Photo credit: PhotoMIX Company