What is 5W-40 engine oil suitable for?

The 5W-40 grade is suitable for a wide range of modern petrol and diesel engines, especially turbocharged and performance models, provided the oil meets the vehicle maker’s specifications. It offers good cold-start performance and solid high-temperature protection, making it a versatile choice in many climates. Always check your owner's manual or service guide to confirm the exact spec required for your engine.

Understanding the 5W-40 rating

Two numbers in an engine oil specification communicate how the oil behaves across temperature ranges. The first number (5W) describes cold-start viscosity, while the second (40) describes viscosity at operating temperature. This combination makes 5W-40 suitable for use in both cold climates and hotter conditions, often in engines that experience higher operating temperatures or turbocharged boost.

What the numbers mean in practice

5W-40 oils flow sufficiently at cold starts to protect engine parts during startup, and they maintain a relatively high viscosity at heat, helping form a protective film between moving components. Many 5W-40 oils are synthetic or synthetic-blend, offering enhanced oxidation resistance and longer drain intervals. However, the numbers alone do not guarantee fit for your engine—the oil must also meet the manufacturer’s approved specifications.

• 5W-40 provides reliable lubrication across a wide temperature range, from cold starts to hot driving conditions.


• Viscosity at 100°C (the 40) helps maintain film strength in high-load or high-temperature scenarios.


• Not all 5W-40 oils are the same; verify that the oil meets the engine’s required API/ACEA specs and OEM approvals.


• Always match the oil to the vehicle’s stated specification, not just the viscosity grade.

Conclusion: The 5W-40 rating is a versatile baseline, but correct application depends on the engine’s specification and the environment.

Where it’s commonly used

Many modern engines—especially European designs and turbocharged powerplants—are designed to accept or require 5W-40, but usage varies by model and year. The following are typical contexts where 5W-40 appears in owner manuals and service recommendations.

Typical engine types and brands

Modern gasoline engines from brands such as Volkswagen Group, BMW, Mercedes-Benz, Audi, and Porsche often specify 5W-40 for certain generations, particularly those with turbocharging or high output. Many diesel engines in passenger cars also list 5W-40 as an acceptable grade in EU markets and other regions where this oil is common.

• Modern turbocharged gasoline engines require robust protection at higher temperatures, where 5W-40 can be advantageous.


• Diesel engines that specify a 5W-40 grade for performance, efficiency, or emissions-compliant operation may use this oil under certain OEM approvals.


• Older engines with OEM-approved tolerances may still accept 5W-40 if specified by the manufacturer.


• Applications span passenger cars, light trucks, and some performance or luxury vehicles.

Conclusion: Always confirm the exact spec in the owner’s manual or with a service adviser, since some engines require a thinner or thicker grade or a different OEM approval.

Key specifications to verify

Beyond the viscosity number, engine oil must meet certain performance and approval standards. The following guidelines help ensure compatibility with your engine’s design and warranty requirements.

API/ACEA ratings

Look for an oil that carries current API service classifications suitable for gasoline or diesel engines (for example, API SP for gasoline engines) and ACEA ratings appropriate to your region and engine (such as A3/B4 for high-performance gasoline engines or C3 for certain modern diesels). The exact combination depends on the engine’s design and emission-control strategy.

• Gasoline engines commonly align with API SP/SN and ACEA A3/B4 classifications.


• Diesel engines may require API CK-4 or newer, and ACEA C3 or other diesel-specific ratings depending on emissions systems.


• Some engines specify OEM approvals in addition to API/ACEA requirements.

Concluding: If in doubt, verify that the oil meets both the generic API/ACEA ratings and the engine’s OEM approvals.

OEM approvals and compatibility

Several manufacturers require specific approvals to back up warranty and performance claims. These approvals ensure the oil meets the engine’s design tolerances and emissions controls.

• MB: Mercedes-Benz 229.5/229.51 for many performance and high-output engines.


• BMW: Longlife approvals such as LL-01 for many gasoline and diesel engines.


• Volkswagen Group: VW 502.00/503.00 (gasoline/diesel) or newer specs depending on model year.


• Porsche: A40 approvals for certain high-performance models.


• Renault/Nissan/Renault RN0700 or RN0710 or equivalent approvals where applicable.


• GM Dexos2 or other OEM-specific approvals may be required for certain regions or models.

Conclusion: OEM approvals are mission-critical for warranty coverage; always verify the exact approvals listed for your vehicle.

Climate and driving conditions

Climate and usage patterns influence whether 5W-40 is the best choice. In some regions, starting with 5W-40 is ideal, while in others a different grade may be preferred for extreme conditions or specific driving styles.

Driving conditions where 5W-40 is advantageous

5W-40 performs well in a broad range of conditions, including cold winters and hot summers, and under mixed-duty driving that includes both daily commuting and highway cruising. It provides reliable startup lubrication and maintains viscosity under sustained loads.

• Cold climates: The 5W component improves cold-start flow, reducing wear during startup.


• Hot climates and high-load driving: The 40-grade helps maintain protective film strength at elevated temperatures.


• Urban stop-and-go with occasional long trips: A versatile choice that covers varied operating temperatures.

Concluding: If you operate in extreme cold or extreme heat, confirm that 5W-40 is recommended for your vehicle; some climates or engines may tolerate or require a different grade.

Summary

5W-40 engine oil is a versatile, multi-grade lubricant widely used across many modern petrol and diesel engines, especially turbocharged and performance-oriented models. The dual-number rating indicates strong cold-start protection and robust high-temperature performance, but the ultimate suitability depends on manufacturer specifications and OEM approvals. Always consult your owner’s manual to confirm the exact grade, API/ACEA ratings, and OEM approvals required for your engine, and consider climate and driving conditions when choosing an oil.

What cars can you use 5w40 oil for?

Fully Synthetic Oil 5W-40 – Mercedes-Benz, VW, Renault, Porsche. Redex 5W-40 is a fully synthetic motor oil that's suitable for use in a range of engines, including Mercedes-Benz, VW, Renault, and Porsche models.

Which is better engine oil, 5w30 or 5w40?

Neither 5w30 nor 5w40 is universally "better"; the right choice depends on your vehicle and climate. 5w30 is better for cold weather and fuel efficiency because it flows more easily when cold, while 5w40 is better for hot climates and demanding conditions like towing or high performance, as it provides a thicker protective film at high temperatures. Always check your vehicle's owner's manual to determine the manufacturer's recommendation, as it is the most important factor. 
This video explains the key differences between 5W30 and 5W40 engine oils: 52sHonest Mechanic ColoradoYouTube · Jan 13, 2024
Choose 5w30 if:

• You live in a colder climate: Its lower viscosity at operating temperature allows for faster lubrication and easier engine startups in cold weather. 
• Fuel efficiency is a priority: 5w30 causes less drag and can lead to better gas mileage. 
• Your engine is a modern gasoline engine: It's the recommended oil for many modern gasoline applications. 

Choose 5w40 if:

• You live in a hot climate: The thicker oil provides better protection under high heat conditions. 
• You frequently tow or carry heavy loads: The thicker oil offers better protection for high-stress situations. 
• You have a high-performance or high-mileage engine: 5w40 can provide better protection and help maintain oil pressure in older or more demanding engines. 
• Your vehicle is a diesel: 5w40 is the suggested oil for most diesel applications. 

This video demonstrates the performance difference between 5W30 and 5W40 engine oil in a diesel engine under heavy load: 1mThe Auto BrainsYouTube · Oct 27, 2025
The bottom line

• Consult your owner's manual: The manufacturer's recommendation is the most crucial factor to consider. 
• Consider your climate: Choose 5w30 for cold climates and 5w40 for hot climates. 
• Consider your driving habits: 5w40 is better for demanding use, while 5w30 is generally suitable for average use and prioritizing fuel economy. 

What happens if I put 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. 

When should you use 5w40?

5w40 is better for starting your engine at low temperatures as it flows more easily at these temperatures.