Can You Mix Fully Synthetic With Semi Synthetic Oil?

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Can you mix fully synthetic with semi synthetic oil? Well, the answer is YES to some extent, but it depends.

While it is generally not advisable to mix oils for your engine, there are situations that may leave you with no choice but to do so. Synthetic oils are recommended for vehicles; it tends to offer more benefits than any other type of car engine oil you may think to use.

On the other hand, conventional oils are also good for car engines, and they have their advantages over synthetics (though not so significant advantages).

Now comes semi-synthetic oils, which is typically a blend of mineral oil and conventional oil. This type of oil (semi-synthetics) is regarded at almost the same level as full/pure synthetic oils; thus, some car owners wish to know if they could mix these oils.

Why Mix Fully Synthetic And Semi Synthetic Oil?

To clearly explain if you can mix fully synthetic with semi synthetic oil, firstly, we need to differentiate these oils, how they vary, and what happens when you mix the two.

Apparently, car engines generate a lot of dirt in the form of carbon, soot, and other stuff – these dirt are a result of combustion, and they are inevitable. However, a good car engine oil flows through the engine and cleans off this dirt that can possibly reduce the engine’s performance and efficiency.

But the big question remains, which car engine oil is capable of cleaning the engine to make it work efficiently and last long?

Fully Synthetic Oils

Full synthetic oils are typically made from refined natural gas; they are well purified and appear to be best for most modern cars that operate in higher temperatures. Generally, full synthetic oils are rated the best for all car engines (old or new).

More so, fully synthetic engine oils are 100% non-conventional, which means that there’s no iota of conventional oil in its formation. The high-performance fluids will definitely remove every deposit generated during combustion and would keep your engine functioning at its finest.

The only challenge that keeps most people away from synthetic oils is the price. Synthetic oils are about 4X costlier than conventional. However, they are worth the price (considering its numerous advantages).

Semi-Synthetic Oils

Would you guess? What is semi synthetic oil? This type of oil is a blend of conventional mineral oil with full synthetic oil. Was your guess correct?

Well, semi synthetic oils are also referred to as synthetic blends. However, while this type of oil contains mineral oil and full synthetic oil, the former (mineral oil) has low volume in the mix.

This literally interprets that semi-synthetic oils can perform better than just mineral oils, but it’s not liable to outperform fully synthetics.

Also, semi synthetics are cheaper than full synthetics – they are very good for your engine and can guarantee a better-performing engine. The mixture of mineral oil and full synthetic delivers a considerable viscosity at a lower price.

Can You Mix Fully Synthetic With Semi Synthetic Oil?

Can You Mix Fully Synthetic and Semi Synthetic Oil

So here’s the big question on most car owner’s mouth – can you mix fully synthetic with semi synthetic oil? Already, the semi synthetic oil isn’t 100% pure – it has been mixed with some other engine oil; hence, it’s already a blend. Going on to mix it again with fully synthetic oil isn’t advisable.

However, the result won’t be bad for your engine; instead, here’s what it would do – the mixed oil won’t offer all the benefits from a full synthetic oil to your engine because the additives in the oils may not be compatible.

But be rest assured that mixing oils (whether synthetic with semi-synthetic or synthetic with mineral oil) won’t cause any detrimental damage.

We would strongly advise that you stick to what’s prescribed by your auto manufacturer. That way, you will always get the most of your engine and won’t have to change oils quite regularly.


There are obviously a lot of myths about mixing oils, but the summary remains that mixing oils isn’t bad – instead, it is just not recommended. So, when next you hear people ask this question, “can you mix fully synthetic and semi synthetic oil?” simply tell them it’s a safe practice but not recommendable.

Finally, remember to wash your car’s engine bay once in a while – it also helps to ensure maximal performance and a long-lasting engine.

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