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Can You Mix Oil Brands? (Quick Facts)

Oil is essential lubrication for your engine. If you don’t put the right oils in your engine it is surely going to malfunction and lose its longevity. However, some oils are pretty expensive, and in emergencies that might not be available near you.

So what could be the solution, can you mix oil, what will be the ultimate outcome. Let’s find out more.

Can you mix oil brands?

Mixing oil brands is a common practice among people. Mixing oils with similar viscosity will be just fine but it does have its downside. There are several additives present in oils and they might react with a different brand of oil. Mixing oil brands has a high chance of total inefficient results.

Is it bad to mix engine oil brands?

When it comes to mixing different engine oils brands it sure does give birth to a lot of confusion and debate. You can say you have always mixed engine oils and never faced any problems.

Or you can say there are always 10 to 20% old oils left in the engine when you are doing an oil change, so why is there so much fuss about mixing engine oil brands, it should be a normal topic, what is there to discuss.

Actually, it was quite easy in the past, you could easily mix different engine oil brands with similar viscosity and get satisfactory results.

However, in modern times there are lots of additives added to the engine oil to increase its longevity, boost its lubrication capabilities, and also make it more weather resistant.

When you mix two different brands of engine oil the additives present in the engine oil have a high probability to react to different elements. It could end up in a total disaster, your mixed engine oils might lose their efficiency and lubrication capabilities.

Ultimately, mixing engine oil brands might end up running your engine and decreasing its longevity. If you are not sure about the outcome of mixing two different oil brands then try to keep it simple and use a basic replacement.

Can you mix synthetic oil brands?

synthetic oils are a highly refined version of regular oil. It contains less adulteration and prevents forming any kind of sludge in your engine. You can also aspect a good amount of weather resistance and efficiency from the synthetic oil.

However, synthetic oils aren’t cheap. If you are thinking about mixing synthetic oil with regular oil to save some cash and also hoping to get some satisfactory results then you can give it a try.

It would be best if you buy a professionally mixed synthetic oil blend, this would ensure a minimum amount of safety to your engine. If you can afford to use only synthetic oil then it would surely be beneficial in the long run.

Can you mix gear oil brands?

If you are using professionally mixed gear oil blends then you can be at ease. But if you are planning to mix gear oil brands on your own then you need to be extra careful. Regular gear oil doesn’t only contain oil, it has various other additives to increase the base oil’s efficiency.

So you are getting a performance boost thanks to the additives but there is a catch, these additives are quite highly reactive.

When you are trying to mix different gear oil brands even if those oils are at the same viscosity, the additives might react with each other and reduce the overall performance efficiency. 

Can you mix diesel oil brands?

Mixing diesel oil brands isn’t an ideal practice but in case of emergency, you can do it. In the past mixing oil brands wasn’t a matter of that much concern but when manufacturers started performance-boosting additives to the oil, mixing oil has become a 50-50 gamble.

You don’t know for sure if the oil mix would be sustainable or a total disaster even if you mixed different diesel oil brands with similar properties. So be very cautious about the additives contained, it shouldn’t be reactive with the diesel oil brand you are trying to mix.

Can you mix different oil brands with the same weight?

When it comes to mixing oil brands their grade, weight and viscosity play a vital role. If you are mixing oils with different weights then it won’t be a proper mix and you won’t get any satisfactory result. The weight and the viscosity of the oil you are mixing should match.

Oil with higher weight will have high viscosity making it thicker, if you mix oil with lower weight and low viscosity with a higher one then the mix won’t be consistent. However, mixing oils has lots of other variables too.

The oil available in the market is not just oil, it’s a mixture of oil and performance-boosting additives. If you are not paying attention to the additives and how they are reacting with other oil brands, all your efforts are sure to go in vain. 

So, yes, you can mix different brands of oils if the weight is the same, but along with that, you have to be careful about the grade, viscosity, and other additives in each brand to make a fruitful outcome.

What happens if you mix car oil brands?

Mixing oil brands require a lot of attention, though there will be only two possible outcomes. Such as –

If it’s a perfect mix:

If the properties of two different oils are suitable for a mix, if they have similar weight, viscosity and are of the same grade then you can hope for satisfactory results.

The performance-boosting additives mixed with the base oil may be a matter of concern but if they don’t show any kind of reaction then you won’t have to worry about mixing the oil. 

If it’s not a perfect mix:

if the properties of two different oils are not similar to each other or the oils have similar properties but the performance-boosting additives are not a suitable match for each other then you are up for a great deal of trouble.

The oil mixture will lose its lubricant capabilities and will be quite inefficient. Using an improper oil mixture is sure to cause sludge build-up in the engine and other related parts.   

Does brand of oil matter? Does it matter if you mix oil brands?

It surely does matter if you are mixing oil brands. Different manufacturers use different performance-boosting additives with base oil to enhance its efficiency, weather resistance, and lubrication capability.

Even if you are mixing two different oil brands with a similar grade, weight, and viscosity, you can not be 100% sure about the outcome.

The performance-boosting additives may remain neutral or end up in a total disaster reacting with each other and reduce the overall efficiency of the oil. So the oil brand and performance-boosting additives matter a lot when you are mixing oils. 

3 reasons why can/can’t you combine oil brands:

You will come to know 3 reasons why you can or can’t combine oil brands after reading this section thoroughly –


If you can not afford highly refined synthetic oil for your engine then using a professionally mixed blend can be your best bet. It would be at a lower price than synthetic oil and will be able to provide satisfactory results. 


Synthetic oils are known for their performance and efficiency. But there are very few people who can afford to use synthetic oils regularly, so the synthetic oils are often mixed with suitable regular oils.

It increases the efficiency of the mix making it more lubricant.


The biggest uncertainty about combining oil brands is about the additives added for performance enhancement. These either stay neutral in a mix or react horribly and ruin the lubrication and overall performance.

Your engine might have to pay a high price if the oil mixture goes wrong. 

What should you do when mixing engine oil from different manufacturers?

Things you should be careful about while mixing engine oils are given below –

Look for similar properties in liquid:

you should always look for oil with a similar grade, similar weight, and viscosity. It will make your mixture more efficient and sustainable. 

Keep an eye on the additives:

See the ingredients list or try to find out what kind of additives are present in the oil. Check out if the chemical components in the mix will react or stay neutral. 

Check for any sludge build-up:

Always check for any sludge build-up while changing old oils. The sludge build is an indicator of how good or bad the oil mixture truly is. If you see sludge build in the engine then changing the oil mixture is necessary.

Can you mix different brands of 5w30 oil? 

5w30 is a multigrade oil. 5 indicates the viscosity of the oil, the ‘W’ represents its weather resistance, mainly winter resistance, and the 30 represents thickness. Now about mixing different brands of 5w30 oils, it can be done without any worries.

Can I mix 5W30 with 10w40? Is it OK to mix 5W30 with 5W40? 

Mixing 5w30 with 10w40 or mixing 5w30 with 5w40 in both cases, the outcome won’t be desirable. 5w30 and 10w40 both have completely different viscosity and thicknesses, it will never be a perfect mix.

If you mix 5w30 with 10w40 it might be a medium thickness and might clump together making the oil hard to flow. Mixing 5w30 with 5w40 can be done but the thickness difference is an issue.

Can you mix Mobil 1 with Castrol? 

If you maintain similar properties in the oil mix, keeping the viscosity, weight, thickness similar for both oils then mixing Mobil 1 with  Castrol can be acceptable.

Why do you mix engine oils? 

It is mostly to reduce the cost of the oil and trying to get a better performing blend. Synthetic oils are the best choice for your engine but they are sold at a pretty high price.

So people try to mix a little bit of synthetic oil with their regular oil to get the most affordable and efficient mixture.

Final Thoughts: 

Mixing oils with a similar grade, weight and viscosity are always encouraged. The people stuck in an emergency or can’t afford high-quality synthetic oils seek an oil mixture with satisfactory performance. Although mixing oils bears a high risk due to the reactive additives present in the oil.