Can you mix 5W30 and 10W40 oil?

Mixing 5W-30 and 10W-40 oil is generally possible, but there are some considerations:

When It Might Be Acceptable:

• If you need to top off your oil and only have 5W-30 or 10W-40 available, mixing them is better than running low on oil.
• If you're in a situation where you need a temporary solution and can’t get the specific oil recommended for your vehicle, mixing can be a practical choice.

Potential Downsides:

• Mixing oils with different viscosities (5W-30 being thinner and 10W-40 being thicker) can result in an intermediate viscosity that might not provide optimal performance or protection.
• The mixed oil may not offer the specific performance characteristics needed for your engine, potentially affecting fuel efficiency, engine protection, or cold-start performance.
• Using a mixture may impact warranty coverage or performance if it deviates significantly from the manufacturer’s recommendations.

Summary:

• Mixing 5W-30 and 10W-40 is generally possible as a temporary measure, but it is not ideal for long-term use.
• For the best engine performance and protection, use the oil viscosity specified by your vehicle manufacturer and avoid mixing different oils whenever possible.

Typical engine oils with the viscosity grades 5W-30 and 10W-40