Can I use 10w40 instead of 5w20 Honda?

Not usually. For most Honda engines, the approved viscosity is 0W-20 or 5W-20, and 10W-40 is not recommended unless your specific model and climate are explicitly allowed by the owner's manual.

Understanding how oil viscosity works and what Honda recommends helps explain why a switch to 10W-40 is generally discouraged and when an exception might be considered.

Understanding viscosity and Honda's specs

Oil viscosity is a measure of how thick the oil is at cold start and at operating temperature. The first number with the W (for winter) indicates cold-start flow; the second number indicates viscosity when the engine is hot. Lower numbers (like 0W-20 and 5W-20) flow more easily during startup and at operating temperature, which can improve fuel economy and reduce engine wear. Honda typically specifies a lightweight viscosity for modern engines to maximize efficiency and lubrication performance.

Honda's recommended viscosities for recent models

Before listing the common recommendations, note that exact grades depend on the engine, model, year, and climate. The following covers typical guidance seen across many recent Honda vehicles. Always verify with your owner's manual or a dealer for your exact vehicle.

• Most modern Honda gasoline engines: SAE 0W-20 or 5W-20, often synthetic, meeting ILSAC/API standards.


• Older Honda engines or special cases (climate-dependent): SAE 5W-30 or 10W-30 may be specified in some manuals, but only if the manual for your exact model allows it.


• 10W-40 is rarely listed as a recommended grade for contemporary Honda engines and is generally not advised unless your specific manual explicitly permits it.

Concluding note: Do not assume 10W-40 is acceptable across Honda models. Always follow the exact specification in your owner's manual or consult a Honda service professional to confirm compatibility with your engine and climate.

Practical steps if you’re considering a switch or only have 10W-40 on hand

Before making a change, consider these guidance points to stay within manufacturer specs and protect your engine.

• Check the owner's manual for the approved viscosity for your engine code and climate. If it lists 0W-20 or 5W-20, use that grade and a Honda-approved or API/ILISAC-compliant oil.


• Avoid using 10W-40 unless the manual explicitly allows it for your model and operating conditions.


• If you must use a different grade temporarily, replace with the recommended viscosity at the next oil change and avoid prolonging use of a non-approved oil.

In practice, switching away from the recommended viscosity can affect fuel economy, cold-start performance, and overall lubrication. When in doubt, consult your local Honda dealer or a qualified technician for a model-specific recommendation.

Summary

For most Honda vehicles, 0W-20 or 5W-20 is the standard recommendation. 10W-40 is not typically approved and can reduce cold-start efficiency and fuel economy, potentially affecting warranty coverage. Always follow the oil viscosity specified in your exact vehicle’s owner's manual, and consult a Honda service professional if you’re unsure.

What happens if I put 10W oil instead of 5W?

Using 10W-30 instead of 5W-30 oil increases oil thickness at low temperatures, reducing flow during cold starts. This can lead to insufficient lubrication, causing increased engine wear and harder startups. To avoid damage, always use the manufacturer-recommended viscosity.

What would happen if I put 10W40 instead of 5w30?

You will consume a little more fuel, have less power if you have a hydraulic VVT system, and a little more wear on each start of the engine. Today's engines are designed carefully for a specific viscosity.

Is it okay to use 10W40 instead of 5w20?

No, you should not use 10W-40 instead of 5W-20, as 10W-40 is a thicker oil that can cause inadequate lubrication, especially during cold starts, and may lead to increased wear in modern engines designed for thinner oil. The engine is designed for the specific viscosity of 5W-20 to ensure proper flow to all components and to meet fuel economy standards, so using a thicker oil can negatively impact performance and protection. 
Potential issues with using 10W-40

• Cold start problems: 10W-40 is thicker in cold temperatures, which means it won't flow as easily or quickly when you start the engine. This can lead to a period of inadequate lubrication and increased wear on vital parts like piston rings and bearings. 
• Reduced fuel efficiency: Modern engines are designed to run on specific, often thinner, oils to improve fuel economy. Using a thicker oil increases internal friction, which can slightly lower fuel efficiency and power. 
• System malfunctions: In some engines, a thicker oil can interfere with the operation of variable valve timing (VVT) systems, preventing them from functioning correctly. 
• Increased strain: Modern engines are built with very tight tolerances. Using a thicker oil can create more friction and heat, potentially leading to more wear over time, especially under high-load conditions. 

Why the manufacturer recommends 5W-20

• Precise design: The recommended viscosity was chosen by the engine's engineers for optimal performance and longevity. 
• Fuel economy standards: Automakers use thinner oils like 5W-20 to help the vehicle meet fuel efficiency targets. 

What to do

• Always use the oil viscosity recommended in your car's owner's manual. 
• If you have already used 10W-40, it's best to change it to the correct 5W-20 as soon as possible. 

What oil can I substitute for 5W-20?

The main alternatives to 5W-20 motor oil are 0W-20 and 5W-30, but always check your owner's manual first to confirm the correct alternative for your vehicle. 0W-20 is a very common substitute as it has the same viscosity at operating temperatures and can offer better fuel economy, while 5W-30 is sometimes recommended for use in hotter climates or for older/high-mileage engines. 
Common 5W-20 alternatives

• 0W-20: This is often the most direct and recommended alternative to 5W-20, especially for newer cars. It provides the same viscosity (resistance to flow) once the engine is warm and is approved by many manufacturers, such as General Motors, as a substitute. 
• 5W-30: This is a slightly thicker oil that may be recommended as an alternative in some manuals, particularly for vehicles driven in very hot climates or for engines with high mileage. Using a 5W-30 oil can offer more protection at high temperatures but may slightly reduce fuel economy compared to 5W-20. 

How to choose the right alternative

1. Consult your owner's manual: This is the most crucial step. Your manual will state the specific oil viscosity recommended for your vehicle and will often list acceptable alternatives for different driving conditions or if a particular oil is unavailable. 
2. Consider your climate and driving habits:
   • If you live in a very hot climate, the slightly thicker 5W-30 might be a better choice for engine protection. 
   • If your car is under warranty, using an unapproved alternative could be a risk, so it's best to stick with the manufacturer's recommendations. 
3. Be aware of potential effects:
   • Using 0W-20: For most vehicles that specify 5W-20, using 0W-20 is a seamless and safe swap, often leading to the same or better performance and fuel economy. 
   • Using 5W-30: While generally safe for many vehicles, using a thicker oil can potentially cause slight changes in performance. Some older engines may experience a slight decrease in fuel economy or even start to make ticking noises because the thicker oil has a harder time flowing through the engine.