Can I put 5W 40 oil in my car?
Yes. In many cars, 5W-40 is an acceptable viscosity if your manual allows it and the oil meets the required specifications.
Understanding whether 5W-40 is appropriate starts with knowing what the grade means. 5W-40 is a multi-grade synthetic oil that behaves like a 5-weight oil in cold starts and a 40-weight oil at operating temperature. It is commonly used in European and turbocharged engines, and in climates with wide temperature ranges. Whether you should use it depends on your engine design, climate, and the specifications set by the manufacturer.
What 5W-40 means and when it's right
The "5W-40" designation indicates low-temperature flow characteristics (the "5W") and high-temperature viscosity (the "40"). This combination provides relatively robust protection during cold starts and stable lubrication at higher engine temperatures. It is widely used in many modern engines, especially European makes and turbocharged setups, but not every engine is rated for this exact grade. Always verify against your vehicle’s requirements.
Notes on climate and engine design
Climate and engine design influence whether 5W-40 is a good choice. In vehicles that specify lighter grades (such as 0W-20 or 5W-30), using 5W-40 may be acceptable only if the manufacturer lists it as an acceptable alternative. Conversely, engines designed for higher-viscosity oils or under heavy-load conditions may benefit from or require 5W-40. The safest path is to follow the owner’s manual and OEM recommendations.
How to verify compatibility with your vehicle
To know if 5W-40 is right for your car, check the official documentation and the oil specification sheet. The following steps help determine compatibility:
- Check the recommended viscosity in the owner's manual (examples: 0W-20, 5W-30, 5W-40).
- Look for the required oil specifications and approvals (such as API, ACEA, OEM-specific approvals from the manufacturer).
- Confirm whether 5W-40 is explicitly listed as an acceptable alternative or as part of a viscosity range allowed by the manufacturer.
- Consider climate and driving conditions (cold winters, hot summers, heavy towing, or frequent short trips).
- Ensure the oil brand and product you choose meets the exact OEM approvals for your engine.
Conclusion: If the manual allows 5W-40 and the oil meets the required specifications, it's safe to use; otherwise, use the recommended grade.
Pros and potential drawbacks of 5W-40
Like any oil choice, 5W-40 has advantages and potential downsides compared with other viscosities:
- Pros: Strong protection at higher operating temperatures, good cold-start performance for many climates, broad availability, and compatibility with many turbocharged engines.
- Cons: Slightly higher viscosity at cold start than some lighter grades, which can impact fuel economy in certain engines; not all engines tolerate higher high-temperature viscosity; some warranties require specific oil grades.
Conclusion: 5W-40 can be a solid choice when it aligns with the car's specifications and driving conditions, but it is not a universal fix for every engine.
Practical steps if you decide to switch
When changing to 5W-40, follow these practical steps to ensure a proper switch:
- Use oil that meets the exact OEM approval requirements for your engine (do not substitute brands or specifications).
- Perform a full oil change and replace the oil filter to remove contaminants and ensure proper circulation.
- Avoid mixing oils of different viscosities or specifications; if you must switch, follow the manufacturer’s guidance or consult a professional.
- Check the oil level after the change and monitor engine temperature and performance in the days following the switch.
- Keep records of the oil grade, approvals, and service date for future reference and warranty considerations.
Conclusion: A careful switch to 5W-40 requires matching OEM approvals, proper service procedures, and monitoring after the change.
Summary
Bottom line: 5W-40 can be used in many cars if the manufacturer approves the viscosity and the oil meets the required specifications. Always consult the owner's manual and a trusted mechanic if you're unsure, and ensure you use an oil that carries the correct OEM approvals. With proper verification and service, switching to 5W-40 can provide reliable protection across a wide range of temperatures.
Is 5W-40 suitable for my car?
Resultantly, 5w40 oils are likely to be used in higher-performance engines that have higher operating temperatures and loads than the norm – those driven in urban environments, that commonly sit in traffic or driven at particularly high speeds, for example.
When should you use 5W40 oil?
5w40 is better for starting your engine at low temperatures as it flows more easily at these temperatures. When the engine is running and hot, 5w40 and 10w40 have high viscosities and are equally effective in protecting against engine wear.
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.
What vehicles use 5W40 oil?
Common Use Cases for 5W-40
- Diesel pickup trucks and Class 8 semis.
- Fleets operating in extreme weather conditions.
- Turbocharged or high-RPM engines.
- Light-duty European diesel or gasoline vehicles that call for mid-SAPS oils.
