Can You Mix 5w30 and 10w30 Oil? (Expert Opinion)

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Mixing two different oils is not advisable, but a lot of drivers do that, and it hasn’t affected their engine yet. Apparently, oils have different viscosity and contain different additives. When you mix oils, most times, the additives in both oils will not blend. So, can you mix 5W30 and 10W30?

It is important that you know the difference(s) between the two oils you’re about to mix up. However, motor oil performs one general function. And that is to lubricate the engine and its components so that the car will work smoothly with friction occurring inside the engine; thus, leading to engine overheating.

Can You Mix 5w30 and 10w30 Oil?

Pouring in 10W30 to an engine that has been running 5W30 is safe and poses no harm. However, you should know that 10W30 has more density than 5W30. The viscosity of these two oils is very close; hence, they might mix perfectly inside the engine; so to say, it is okay to mix 5W30 with 10W30.

Some drivers have alleged that they poured in 10W30 without draining the remaining 5W30 in their engine, and yet nothing happened.

However, we’d love to let you know that using one particular oil for your engine offers more benefits than DIY blends or regular change between oil types.

When you mix two different oils; whether you’re mixing synthetic with conventional oil, or you’re mixing two oils of different viscosities, it doesn’t pose any harm to your engine, but it can cost you a few important things you may not have wanted to lose.

Also, two oils of the same weight but different viscosities would be the same at operating temperature, but they’d differ when cold. The less viscous/thinner one will flow easily to the top ends.

What Happens When You Mix 5W30 with 10W30?

What Happens When You Mix 5W30 with 10W30

Well, it’s not just about mixing 5W30 and 10W30. Generally, when you mix any two different oils (whether they differ by type or viscosity), it tends to reduce your engine’s performance and decreases the gap between oil changes.

This is because the additives in the oil will not blend; thus, your engine won’t get the most of either of the oils. Also, at low temperatures, the viscosities of these oils will differ, and your engine components may not get the full benefits of the oils.

5W30 thickens less when cold and flows easily to top ends. In contrast, 10W30 is actually meant for engines that carry heavier loads, so it is thicker when cold.

However, this does not trigger any damage to your engine, and it does not mean your engine would breakdown because you mixed two oils. In most cases, the worst scenario is losing warranty coverage.

For example, if your car manual indicates that you should only use 5W30 or 10W30 if you mix oils, you are likely to void the warranty, and that leaves you fully in charge of all repairs to your vehicle. Well, if your warranty has expired already, you may not be bothered about this effect.

Frequently Asked Questions

Can you mix 5w30 and 10w30 oil?

Yes, you can mix 5w30 and 10w30 oil. They are both multi-grade oils and are compatible with each other.

Is it safe to mix different types of engine oils?

Mixing different types of engine oils is generally not recommended as it can affect the viscosity and performance of the oil. However, mixing oils of the same viscosity and API rating is generally safe.

Will mixing 5w30 and 10w30 oil affect my engine’s performance?

Mixing 5w30 and 10w30 oil of the same API rating and viscosity is unlikely to affect your engine’s performance. However, it’s always best to use the manufacturer’s recommended oil to ensure optimal performance.

Can I mix synthetic and conventional oils?

Yes, you can mix synthetic and conventional oils. However, it’s generally not recommended as it can affect the performance of the oil. It’s best to use one type of oil to ensure optimal performance.

What should I do if I accidentally mix different types of engine oils?

If you accidentally mix different types of engine oils, it’s best to have your oil changed as soon as possible to avoid any potential damage to your engine. Mixing different types of oil can affect the viscosity and performance of the oil, which can result in engine damage.


Can you mix 5W30 and 10W30?  The simple answer is YES; you can mix the two oils; not just because they have the same weight, but because it is safe to mix two different engine oils. However, we do not encourage the mixing of motor oils. Why? Because the act does not guarantee any advantage over using one type of oil.

Also, if your car is still under warranty, mixing oils is liable to void the manufacturer’s coverage on potentially expensive repairs. But if you’re stuck with no other choice, then you can go ahead to pour in that 10W30 into your engine that has been running 5W30.

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