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Can I Mix 10W 30 With 5W 30?

Can I Mix 10W 30 With 5W 30

Motor oil isn’t just the blood of your engine; it’s more like the life force that enables all the parts to function harmoniously. It’s crucial to keep your oil at the right level and to ensure it maintains the correct viscosity for your engine.

But what happens if you realize you’ve got two types of oil in your garage, with slightly different viscosities? Can I mix 10W 30 with 5W 30? Is it a catastrophic mistake, or will it keep your engine running as smoothly as ever? Let’s delve into the world of engine oils and demystify this common dilemma.

Can I Mix 10W 30 With 5W 30?

No, It’s not recommended to mix different viscosity oils like 10W-30 and 5W-30, in an emergency, a temporary mix is unlikely to cause immediate harm. However, it’s advisable to change the oil to the correct viscosity at the earliest convenience for optimal engine performance.

The practical answer to this question is complex yet simple. Yes, it is technically possible to mix 10W-30 with 5W-30. However, the deeper you go, the more you’ll find that although this combination may not spell disaster for your car, it’s not the ideal scenario either.

Differences Between 10W 30 And 5W 30

Viscosity is the most critical aspect when it comes to engine oil. It refers to the oil’s resistance to flow, or in layman’s terms, how thick the oil is. The ‘W’ in the oil grade stands for ‘winter,’ and the preceding number (e.g., 5W) indicates the oil’s cold-weather flow, which is crucial for starting your engine in frigid temperatures. The second number (e.g., 30) reflects the oil’s viscosity at operating temperature.

So when you compare 5W-30 and 10W-30:

Effects Of Mixing 10W-30 With 5W-30

Mixing oil viscosities in general might not harm your engine right away, but it’s not a risk you should be keen on taking. Here’s what could happen:

Expert Opinions

Mechanics and automotive experts often warn against mixing oils of different viscosities due to the potential long-term issues they can cause. The gamble of blended viscosities is not worth the potential costs down the road.

Practical Tips

If you have no option but to mix oils, remember these practical tips:

Motor Oil Change

Regular oil changes are vital to your engine’s health. Synthetic high-mileage oils may even be preferred due to their extended life and better performance. This is why it’s important to take the opportunity of an oil change to ensure you have only uniform oil in your engine.

Real-World Experiences

In the real world, people do mix oils due to necessity or simple oversight. Not everyone faces engine destruction the next day.

However, sometimes, mixing oils isn’t as catastrophic as it seems. In a pinch, topping off with a different grade is better than running your engine low on oil. But it should be a practice left for emergencies.

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What Happens If You Put 10W Oil In 5W?

When you substitute a 10W oil for a 5W oil, you’re using an oil with a higher viscosity in cold temperatures, which means it will be thicker when the engine is cold. While this might not cause immediate damage, it can lead to sub-optimal engine performance, especially during start-up. 

In colder climates, this can result in increased resistance during engine start-up, making it harder for the engine to turn over and potentially causing additional wear on the engine components. It’s crucial to use the engine oil viscosity recommended by the vehicle’s manufacturer to ensure optimal engine health and performance.

What Happens If You Mix 10W-40 With 5W-30?

Mixing 10W-40 oil with 5W-30 oil can result in several unpredictable outcomes since the blend’s properties may vary from the individual attributes of each oil. The hybrid oil might achieve a viscosity that lies between the two original oils, potentially leading to adequate performance under certain conditions. 

However, this practice is not typically recommended by engine manufacturers, as the specific viscosity gradations, including their temperature ranges and lubricating properties, are carefully designed for optimal engine performance. Mixing of 5w-20 and 0w-20 can provide different but unwanted results.

Is It OK to talk to Different Grades Of Engine Oil?

Oils are designed to work within specific temperature ranges and have particular properties that maintain engine efficiency and longevity. When different grades are mixed, it may dilute or alter these properties, affecting the oil’s ability to protect and lubricate the engine effectively. 

The result can be suboptimal performance, increased engine wear, and potentially reduced engine life. It’s always best to consult your vehicle’s owner manual or an automotive professional for advice on the appropriate oil grade for your engine and to stick to it unless otherwise directed.


Ideally, stick to the oil grade recommended by your manufacturer. In cases of emergency, a top-up with the ‘wrong’ oil’s viscosity is acceptable, but be sure to change the oil as soon as possible. Explore whether can i mix 10w 30 with 5w 30. Your car’s longevity may depend on the life force running through its engine, so don’t gamble with its health. And if you’re unsure about any aspect of your car’s care, consult with a professional. Your engine – and your wallet – will thank you in the long run.


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