Which engine oil is better 5W30 or 5W40?

When it comes to engine oil, the choice between 5W30 and 5W40 can be a bit confusing. Both are popular viscosity grades, but which one is better for your vehicle? In this article, we'll explore the key differences between these two engine oils and help you determine which one is the better choice.

What Do the Numbers Mean?

The numbers in the engine oil viscosity grades, such as 5W30 and 5W40, refer to the oil's thickness or resistance to flow. The first number (5 in both cases) indicates the oil's viscosity at low temperatures, while the second number (30 or 40) represents the oil's viscosity at higher operating temperatures.

The "W" stands for "winter," meaning the oil is suitable for use in colder climates. The lower the first number, the better the oil will flow in cold weather, making it easier to start your engine in the morning.

Key Differences Between 5W30 and 5W40

• Viscosity: 5W40 oil is slightly thicker than 5W30, meaning it provides better protection for the engine at higher temperatures. This can be beneficial in hot climates or for vehicles that experience high-stress conditions, such as towing or hauling heavy loads.


• Fuel Efficiency: 5W30 oil is generally considered more fuel-efficient than 5W40, as the thinner oil requires less energy to circulate through the engine. This can result in slightly better fuel economy for vehicles using 5W30 oil.


• Engine Wear Protection: The thicker 5W40 oil may provide slightly better protection against engine wear, especially in high-performance or high-mileage engines. However, the difference is often minimal, and both oils can provide excellent protection when used as recommended.

It's important to note that the recommended oil viscosity for your vehicle can vary based on the manufacturer's specifications, the age and mileage of the engine, and the climate in which you operate the vehicle. Always refer to your owner's manual or consult with a professional mechanic to determine the best oil for your specific needs.

Conclusion

In summary, both 5W30 and 5W40 engine oils are excellent choices, and the decision ultimately comes down to your specific vehicle and driving conditions. If you live in a hot climate or frequently tow heavy loads, 5W40 may be the better option. If fuel efficiency is a priority, 5W30 may be the way to go. Whichever you choose, be sure to follow the manufacturer's recommendations and maintain a regular oil change schedule to keep your engine running at its best.

Is 5w40 better than 5W30 for high mileage?

For a high mileage engine, 5W-40 is often recommended because its higher viscosity can better protect older engines with wider tolerances by reducing leaks, wear, and oil consumption. However, 5W-30 is still a viable option and provides better fuel efficiency due to its lower viscosity, especially in milder climates. Always consult your owner's manual for the manufacturer's specific recommendation, as using an incorrect oil weight can potentially cause issues.
 
5W-40 high mileage 

• Best for: Older vehicles, engines with high mileage, hot climates, and vehicles that undergo high-stress conditions like towing. 
• Benefits:
  • The thicker consistency can help reduce oil consumption and leaks in older engines with wider tolerances. 
  • Provides better protection against wear and tear and maintains oil pressure in older engines. 
• Drawbacks:
  • Can lead to slightly worse fuel economy because it requires more energy to lubricate the engine parts. 
  • May be harder to pump to the turbocharger in some engines. 

5W-30

• Best for: New vehicles, milder climates, and prioritizing fuel efficiency. 
• Benefits:
  • Better fuel economy and potentially quicker lubrication during cold starts. 
• Drawbacks:
  • Less protection against oil leaks and consumption in high-mileage engines. 
  • Can break down faster under high temperatures compared to 5W-40. 

You can watch this video to learn the difference between 5W30 and 5W40 oil: 52sHonest Mechanic ColoradoYouTube · Jan 13, 2024
How to decide

• Check the owner's manual: This is the most important step, as the manufacturer has determined the correct viscosity for your specific engine. 
• Consider your climate: If you live in a hot climate, 5W-40 is generally a better choice for high-mileage engines. If you live in a milder climate, 5W-30 is often sufficient. 
• Think about engine condition: If your engine is already consuming oil or has known leaks, the thicker 5W-40 is more likely to help. 
• Prioritize fuel economy: If your vehicle is relatively newer and your priority is fuel efficiency, 5W-30 is the better choice. 

What will happen if I use 5w40 instead of 5W30?

Putting 5W-40 instead of 5W-30 will result in slightly decreased fuel efficiency and potential performance issues, but is unlikely to cause major damage, especially in warmer climates or for older engines. The main difference is that 5W-40 oil is thicker at operating temperature, which can slightly increase friction and oil pressure. It's always best to follow the manufacturer's recommendation, which is found in your owner's manual or on the oil fill cap. 
What to expect

• Slightly reduced fuel economy: Thicker oil creates more drag on engine components, leading to a small decrease in fuel efficiency. 
• Potential performance impact: A thicker oil may slightly reduce high-end horsepower. 
• Increased oil pressure: 5W-40 has higher viscosity, which can lead to higher oil pressure readings. 
• Potential benefit for older engines: A thicker oil may be beneficial for older, high-mileage engines that have increased wear and tear, as it can help maintain oil pressure. 
• No harm in cold starts: The "5W" rating is the same for both oils, meaning both will have similar flow characteristics during cold starts. 

When to be cautious

• Modern engines: Modern engines are designed with precise tolerances, and using a thicker oil can cause problems that the manufacturer did not design for, so it is best to stick with the recommended 5W-30. 
• Warranty issues: Using an oil that does not meet the manufacturer's specifications can potentially void your warranty. 
• Stop-and-go traffic: If your engine runs hot in stop-and-go traffic, the thicker oil could be a benefit. 

Best practices

• Check your owner's manual: The manufacturer's recommendation is the safest guide. Check the manual for the correct oil viscosity and specifications. 
• Don't switch for "just because": There's no need to switch from 5W-30 to 5W-40 unless you have a specific reason, such as a high-mileage engine or a preference for heavier oil in a hot climate. 
• Stick to a single type: If you do switch, make sure to use the new oil at your next oil change, as mixing different viscosities is not ideal. 

What are the benefits of using 5w40?

Some of the benefits of using 5W40 oil include:

• Improved fuel economy.
• Enhanced engine performance.
• Protection against wear and tear.
• Corrosion resistance.
• Oxidation resistance.

Which engine oil is best, 5W30 or 5w40?

5W30 engine oils has a narrower temperature range then 5W40. 5W30 is suitable for operating temperature between -25°C and 25°C, and 5W40 has a range of between -25°C and 35°C. In terms of oil flow, 5W30 has greater flow than 5W40. However, for providing higher pressure, 5W40 is superior.