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Can You Mix Synthetic Oil With Regular Oil?

Can You Mix Synthetic Oil With Regular Oil?

Almost every car owner has encountered this question once in their life. Can you mix synthetic and regular engine oil?

Well, there are car owners who believed that mixing the two kinds of oil could potentially harm your engine. If it’s performed multiple times, it could cause severe problems in the engine.

Other people are proactive in mixing engine oil into your car. According to them, combining two different types of oil is fine, and it will not cause any harm to your engine.

I know what you are already thinking about, ‘Which of them is right?’, right?

Today we will be discussing a topic that has been going on for months and even for years, can you mix synthetic and regular engine oil?

Before we go more in-depth with our discussion, let us first understand the two types of oil that are involved in this topic. Read also: 0w20 vs 5w20 oil.

What Is Synthetic Oil?

What Is Synthetic Oil

It is a type of oil that is made out of products that are chemically manufactured in a factory. These synthetic oils, specifically those polyalphaolefins (PAO) and esters have the same qualities as crude oil.

Through a thorough chemical process, engineers have total control of the molecular structure of the polyalphaolefins and esters. The process ensures that the product oils have stable and uniform properties.

This improves the oil’s capability to lubricate the inside of the engine.

So basically, it is an engine oil created by man to be a substitute oil to conventional oil.


Molecular Consistency

It is one of the significant advantages of synthetic oils. The molecules in this oil have almost the same length as each other, which leads to less friction with the different parts of the engine.

If there is less friction happening inside the engine, it significantly increases its lifespan. With no friction, engines can efficiently function when used.

High-Temperature Resistant

Synthetic oils work well even under high temperatures. Engineers and scientists created it to have a better heat transferring capability than any regular oils.

Despite high temperatures, synthetic oil doesn’t breakdown and causes any issues to the engine. But instead, it helps the engine run smoothly even when used heavily.


Synthetic oils are engineered to be stronger than regular oils. It is more resistant to disintegration, which makes its drain interval to be longer than conventional engine oil. With that in mind, it reduces how frequently you’ll be changing your engine oil, which saves you a fortune.



One of the downsides of synthetic oils is they are expensive. If you try to look at it, their price is twice as much as the price of regular conventional oil. Despite its price, it can take care of your engine and improve its lifespan. In other words, they are cost-efficient.

Risky for Old Cars

What I mean by this, using synthetic engine oil on cars that are manufactured before the year 1990 could raise some problems. This type of oil melts down the old sludges inside the engine. However, these sludge serves as a seal on the engine. If they are melted away, oils could leak out from the engine.

What is Regular Oil?

regular oil

Regular oil, or also known as conventional oil, is just pure crude oil with additives to increase the heat tolerance of the machine and to improve lubrication. Regular oil contains natural contaminants such as silicone, waxes, and paraffin.

Compared to synthetic oil, regular oil is a much cheaper option. Despite its lower price, it can still do its job successfully without any issues.

Several people still use regular oil even if it can harm the environment. One reason why people don’t want to refrain on using it because it is more cheaper than synthetic oil.



Regular oil is far cheaper than its counterpart – synthetic oil. Its price range may be up to 3 times less expensive than synthetic engine oil.


Harmful to the Ecosystem

Conventional engine oil cannot be broken into its smaller molecule naturally. With that said, it will not disappear like any organic waste after it is being used. When it is disposed of, it will leave a toxic sludge in that area.


Since all of our car engines today depend on oil, there has been a scarcity of conventional oil in the market. If this continues, prices of oil will also inflate as the supply decreases.

Sensitive to temperatures

Conventional oils reduce its lubrication with it being exposed to extreme cold, and it also breakdown faster when it is exposed to extreme heat.

Can you mix synthetic oil with regular oil?

synthetic oil with regular oil - can you mix them?There is no actual danger when mixing synthetic and conventional oil. There are no proven issues when mixing synthetic oil with regular oil. Gel formations due to chemical reactions of the two substances don’t have a strong basis that this would happen.

The only problem here is that synthetic oil effectiveness is reduced by regular oil. 

Still, it is not advised to always mix synthetic oil with regular oil.


The additive of the two oils may interact inside the engine and get destabilized. Which then reduces the effectiveness of the additives of the two oils.

It would be just a waste of your money. Though it will not harm your car engine, it can reduce your car’s performance.


It is only advisable to mix two types of oils in case of an emergency. For example, you went to a gas station and found out that you are about a quart low on your engine oil.

However, the gas station ran out of conventional oil, and they only have synthetic car oils. Situations like this one are valid for mixing two types of oil.

So if your car runs on synthetic oil, it’s better to stick to it. Why? For you to maximize the benefits of the oil rather than adding a regular oil and reducing its effectiveness. And if you are already using the best engine oil, why add something that is less superior to it?

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