Mixing 5W30 with 5W40: Does it Harm the Engine?

Engine oil plays a crucial role in maintaining the performance and longevity of an engine. It ensures proper lubrication and helps prevent excessive wear and tear. However, what happens if you need to top up your engine with oil of a slightly different grade? Specifically, adding 1 liter of 5W-30 to your existing 5 liters of 5W-40. Does this mix harm your engine, or is it safe to continue driving?

Understanding Oil Viscosity

Viscosity is a measure of a fluid's thickness or resistance to flow. Automotive oils are classified by their viscosity, indicated by numbers like 5W30 or 5W40. The '5W' in these numbers is the viscosity grade, which represents the oil's thickness at a specific temperature. The lower the first number, the thinner the oil. In our case, 5W30 is thinner than 5W40.

When you mix 5W30 with 5W40, the resulting oil mixture will have a viscosity that falls somewhere between the two grades. This does not necessarily harm the engine, as auto engines are designed to operate over a range of viscosities depending on temperature changes.

Impact on Engine Lubrication

Adding 1 liter of 5W30 to 5 liters of 5W40 will make the oil in your engine slightly thinner. While a slight change in viscosity might not be ideal, it is unlikely to cause significant issues for the engine. However, it is not the optimal scenario as a thinner oil provides less lubrication compared to a thicker oil. This can result in increased wear on engine components. Nevertheless, the amount of wear is likely to be minimal as the oil is constantly circulating and mixing.

No Immediate Harm, But Investigate the Issue

While adding the extra 1 liter of 5W30 may not harm your engine immediately, it is important to investigate why the oil level dropped by a liter. If this is a sudden and significant drop, there may be an underlying issue such as a leak. It is recommended to address this issue promptly by consulting a professional to diagnose and fix any potential leaks.

Preventive Measures

To avoid similar issues in the future, it is advisable to carry some oil of the right specification with you in case you need to top up. Regularly checking and changing the oil according to the manufacturer's recommendations is crucial. Additionally, mixing different grades of oil is generally not recommended as it can affect the oil's performance and may lead to premature wear and tear.

Conclusion

Adding 1 liter of 5W30 to 5 liters of 5W40 will not harm your engine in the short term, but it is important to investigate the cause of the oil level drop and address any potential issues promptly. If you are unsure about the specific needs of your engine, always consult a professional mechanic to ensure the best possible maintenance for your vehicle.