Can You Mix Full Synthetic Oil With Synthetic Blend? – Vehicle Freak

Is it time to add more oil to your car engine? If you are just topping off the existing oil, you may be wondering if it is safe to mix different types of engine oil together. Can you mix full synthetic oil with a synthetic blend?

Mixing full synthetic oil with a synthetic blend is possible and won’t cause any harm to a vehicle’s engine. However, the best practice is to just use one type of engine oil, as full synthetic oil is better and its benefits may be reduced when a synthetic blend is added.

Different Types of Engine Oil

Pouring oil to car engine, close up

Oil is the life source of your car’s engine. Without the correct oil, the engine will not run as it should and a car without oil is just as useless as a car without fuel in the tank. There are three different types of engine oil in use today, which we’ll talk about in the next sections.

Conventional/Regular Motor Oil

Conventional oil is the type traditionally used to lubricate motor engines. This oil is also known as crude oil and is naturally occurring on the earth. Before the crude oil is poured into your car engine, it must first go through a refining process.

Conventional oil may be the most natural engine oil available, but several additives are used to ensure the product meets industry standards and don’t damage any of the engine parts.

Full Synthetic Oil

Synthetic oil is man-made in a laboratory, instead of being removed from the earth. Fully synthetic oil is made using different base oils to conventional engine oil and the ingredients are refined and processed to create a high-quality engine lubricant.

This is often considered to be the best engine oil available and different blends are available to provide different benefits. For example, there are synthetic oils that improve performance, protect the engine and work better at high speeds or low temperatures.

Synthetic Blend Oil

Synthetic blend oil is a mix of both conventional and synthetic oil. These oils will often have more additives than conventional oil but not as many as fully synthetic oil.

Synthetic blend oils often will provide better performance than traditional crude oils but will not be as high quality as fully synthetic oils.

When changing your car’s engine oil, it is important that you use the correct type for your engine. Different oil products have different grades and contain different blends of additives, minerals, and base oils.

Different oils have different viscosity grades and will provide varying levels of engine protection. If you are not sure which oil your engine needs, this information should be available in your car owner’s manual.

Can You Mix Full Synthetic Oil With a Synthetic Blend?

Fully synthetic oil can be expensive and some drivers choose to mix a cheaper blend with their existing oil. Mixing a synthetic oil blend with a fully synthetic oil will not damage your car and fully, blended or conventional oils are all compatible with modern engines.

Synthetic oils and synthetic blends often have the same additives but the quality of the ingredients will be higher in fully synthetic oil. As a synthetic blend includes conventional crude oil, there will likely be more impurities than in a completely man-made oil.

When full synthetic oil is mixed with a synthetic blend, the quality of the completely synthetic product will be minimized. The ingredients and additives in the higher-quality oil will be diluted when a blend is mixed and you may not get the premium engine performance and protection you were hoping for.

Occasionally mixing fully synthetic and synthetic blend oil together is fine, but drivers should not make a habit of it. While these oils are made using the same base oils, their formula can vary and the ingredients may counteract each other. Combining blended and full synthetic oil can cause the oil to become weakened and not work as well as it should over time.

Is Fully Synthetic Oil Really Better?

Side view of young man checking engine oil

Using conventional oil will not harm your engine, it’s perfectly safe to continue to use this more traditional method to lubricate your vehicle. However, if you want an oil with added benefits, an oil designed to boost your car’s performance, nothing beats a fully synthetic motor oil.

Fully synthetic oils have many advantages, including:

  • Keeping the engine cleaner.
  • Providing a better flow of oil in colder temperatures.
  • Protecting against engine wear and tear.
  • Better performance in turbocharged engines.
  • Added protection at high temperatures.
  • Longer oil change intervals.

If your car has always used conventional oil, you can switch to fully synthetic oil and experience all of the added benefits. However, different engines need different oils so it is also important to check the grade and viscosity of a product before adding it to your engine.

Benefits of Synthetic Blend Motor Oils

Fully synthetic oils may be the best choice for vehicle performance, but synthetic blends also have their own benefits. If you do not feel like a fully synthetic oil is necessary for your car’s engine or that conventional oil is not good enough, a synthetic blend can work as an effective middle ground.

Here are the advantages of using synthetic blend oil:

  • More affordable than fully synthetic oil.
  • Better fuel economy than conventional oil.
  • Longer change intervals than with conventional oil.
  • Works well for SUVs and trucks.
  • The cheaper cost keeps the price of regular oil changes low.
  • Provides more engine protection than conventional oil.
  • Can better withstand extreme temperatures.

Can Fully Synthetic Oil Last 2 Years? – Oil Change Intervals

There is no denying that fully synthetic oil is superior to other oil types and is the best option for high-performance vehicles. One of the many advantages of synthetic oil is that it doesn’t need to be changed as often as conventional or synthetic blends.

That being said, fully synthetic oil will not last as long as 2 years, this is just a myth. Here are the average change intervals for the different types of oil:

  • Conventional oil will need to be changed approximately every 3000 – 5000 miles.
  • Synthetic blend oils should be changed every 7500 miles. Depending on the quality, a longer period between oil changes may be possible.
  • Fully synthetic oil lasts the longest and will need to be changed every 10000 – 15000 miles, on average.

To find out how long you should leave between oil changes for your car’s engine, check your owner’s manual. Different brands of oil will have differing change intervals and it is important you never wait too long to change a car’s engine oil.

Old dirty oil can become thick and will not be able to lubricate the engine as well as it should. This can lead to engine parts overheating and premature wear and tear. Oil changes are part of a car’s basic maintenance and should never be ignored.


Drivers can mix full synthetic oil with synthetic blend oils. There are many benefits to using fully synthetic oils but occasionally mixing a synthetic blend will not cause any problems for your vehicle.

The biggest issue with mixing these two types of oil together is that the benefits of fully synthetic oil may be reduced. As synthetic blends use crude oil in the formula, there can be impurities that impact the added protection provided by fully synthetic oils.

Before mixing different oils together, it is important to check that the products are compatible with your vehicle’s engine. For more information about what oil to use and how often to change your car’s engine oil, consult your vehicle owner’s manual.

Here are some articles that might interest you:

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Why Are BMW Oil Changes so Expensive? (How to Reduce Cost)

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