5W30 and 5W40: what are the differences and which one should you choose?

Introduction

The performance of the lubrication system directly affects engine lifespan. That is why many motorists wonder which oil viscosity to choose to ensure the engine is fully protected.

What is viscosity?

Viscosity is the measure of a fluid's resistance to flow. For engine oils, it is expressed by two numbers, such as 5W-30 or 5W-40.

• The first number (5W) indicates cold viscosity. The "W" stands for "Winter". The lower this number, the more fluid the oil remains in cold weather.
• The second number (30 or 40) indicates hot viscosity, that is to say when the engine reaches its operating temperature.

5W-30 vs 5W-40: the differences

The main difference lies in high-temperature viscosity:

• 5W-30 : More fluid oil when hot, better fuel economy, recommended for newer engines.
• 5W-40 : Thicker oil when hot, better protection for older or high-mileage engines.

How do you choose?

The choice depends on several factors:

1. Check your vehicle's handbook
2. Take your engine's mileage into account
3. Consider the weather conditions in your area
4. Follow the manufacturer's specifications

Conclusion

As a general rule, always follow the manufacturer's recommendations. If your vehicle has high mileage and you notice oil consumption, switching to a slightly thicker oil may be beneficial.