Should You Mix Synthetic Oil & Regular (Conventional) Oil ?

Can You Mix Synthetic Oil & Regular Oil (Conventional oil)?


Have you ever wondered if you can mix synthetic oil with regular conventional motor oil or vice versa?

Imagine. You are out on an off-road trip and you realize that your car has a lower oil level and as you approach the gas or petrol station and enquire about the oil, you find out they don’t have the oil you normally use. 

For example, let us consider you use synthetic oil and all the store has is conventional oil. Or let’s say you drive an old car, and your oil levels reduce over the period of time.

When you go for regular maintenance, you find out that your oil level is low, but most of the oil from the previous batch is good enough. So it’s not an economical option to drain all the previous oil and replace it with the new one,

Your mechanic may suggest to you that you top up only, the amount which is required to fulfill the recommended oil level.

Now, does that harm your car if you mix them both to get the engine oil to the normal level, or do you have to flush out the existing oil before you add the conventional oil to your car engine?

The short answer for Should You Mix Regular Oil and Synthetic Oil is Yes. You can mix them both – there are exceptions but more about that later.

For a long and clear understanding of this, let’s put on our geek hats and get into this. Let us understand the difference between standard oil (also known as conventional oil or mineral oil) and Synthetic oil.

What is Regular/ Standard/ Conventional Engine Oil?

Regular - Conventional - Mineral Engine Oil

Some other names for standard oil are conventional motor oil, regular motor oil, and mineral oil. 

The standard oil for an engine is made from crude oil. And, it is not a very refined or pure form of oil. Moreover, it is not processed so that it does not perform better in extreme conditions, like high temperatures or extremely low temperatures. 

  • It is thicker/ dense, that’s why it flows slowly in the engine
  • Mineral oil gives less performance boost compared to synthetic oil
  • Mineral oil is kind of older version of current advanced Engine oils

What is Synthetic Engine Oil?

Synthetic engine oil cans

Synthetic oil is also made out of crude oil. The major difference is that synthetic oil is processed to perform better. Synthetic oil has more chemicals added to it, this makes the oil more compatible for different conditions. 

  • For instance, synthetic oil can perform better in high-temperatures and low-temperatures.
  • The lubrication in synthetic oil is better when compared to conventional oil.
  • It contains added chemicals such as detergents & dispersants to keep the engine clean
  • It also has increased thermal & oxidation stability
    It has a higher resistance to oil film breakdown
  • It controls vaporization & consumption even at extreme conditions
  • Improved viscometric properties ensure performance both in cold & hot condition
  • Synthetic Oil has different grades such as 0W30, 0W40, 5W20, 5W30, 5W40, 10W30, 10W40, 15W20, 15W40, 20W50 etc. Depending on how well they perform on different temperatures.

Should You Mix Synthetic Oil and Standard (Conventional) Oil?

mix synthetic and regular engine oil

As we discussed above, this is a huge confusion more car drivers and travelers have. Can you mix standard oil with synthetic oil?

Yes. You can mix conventional oil with synthetic oil. It does not harm the engine. The primary work of the engine oil is to reduce the friction in the engine and maintain lubrication. When there is a reduction in the levels of engine oil, it can be covered with another type of oil.

However, there are some important considerations. 

  • It’s better to match the viscosity of the oils being mixed
  • It’s better to have the same brand of both oils
  • The interval for changing/replacing the oil will be different than mentioned on the oil box or the manual
  • It is not recommended to mix the oils, unless it is urgent, because the effect of this will result in the decreased performance of the engine.

Our Recommendations about mixing two kinds of engine oils

When the oil engine levels are low, your first priority should be to get the oil at the recommended level. Because if your car’s engine oil levels are low, this will result in more problems.

Riding your car on the low engine oil could damage the parts of the engine, causing serious expenses and bigger problems. So, if the oil of the car is below the required level please add engine oil (whether mixed or single do not worry much). Because a low level of oil is dangerous.

Also, if it is not urgent then please consider replacing it with one particular oil, i.e. whichever oil you normally, or better Fully Synthetic oil use.

Also, check out our Full range of Synthetic & Mineral Oil Swiftec

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