Can You Mix Full Synthetic Oil With Synthetic Blend?

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Can You Mix Full Synthetic Oil With Synthetic Blend?


You can mix full synthetic oil with the synthetic blend, as both are chemically compatible. However, doing so will lessen the benefits of the full synthetic oil (better extreme-temperature performance, fuel efficiency, and drain intervals).

Your vehicle’s engine has a lot of inner components.

Many of these components frequently make contact with each other (crankshaft and rod bearings, pistons and cylinder walls, etc.) at high speeds, which can result in them being worn out prematurely due to friction and overheating.

This is where the engine oil comes into the picture.

What is Engine Oil?

It’s a fluid that acts as a lubricant between those moving parts. It minimizes the direct contact between those parts, reducing wear and tear due to less friction – enabling them to operate smoothly.

Apart from this, the engine oil also helps in keeping the engine cooler.

As it circulates throughout the engine, the engine oil absorbs the heat generated by the friction. Then, the heated oil flows to cooler areas of the engine, transferring and dissipating the absorbed heat, resulting in a cooler engine.

Other engine oil uses include protecting the engine against corrosion, sealing the gaps between the piston and cylinder, and cleaning the engine (by removing debris and contaminations).

Different Types of Engine Oil

There are three types of engine oils available in the market these days.

Conventional Oil

Conventional motor oil is based on refined crude oil. The crude oil goes through a series of processes that remove impurities and adjust its viscosity – and you get conventional oil in the end.

This type of oil is liked by many due to its lower price and wide availability – you can find it at any auto parts store.

On the other hand, the main issue with conventional oil is the changing viscosity related to weather conditions. In cold weather, it flows slower than synthetic oil, which affects its ability to lubricate the engine.

In hot weather, this oil can become thinner and lose its ability to maintain a protective layer between the engine’s moving parts. This can result in friction, wear, a higher chance of thermal breakdown, and the eventual formation of sludge and deposits.

Synthetic Oil

Synthetic oil is developed from base oils that are synthesized from specific petrochemicals. This oil comes with a more unified molecular structure, which results in a uniform composition and fewer impurities. In addition to this, certain additives (detergents, antioxidants, etc.) are added to give it extra capabilities.

Due to this improved molecular structure, the synthetic oil can maintain its viscosity during both cold and hot conditions, allowing it to lubricate the engine at the start (when it’s cold) and at the operating stage (when it’s hot).

It’s also more resistant to oxidation than conventional oil, resulting in less sludge formation and better engine performance.

Other advantages of synthetic oil include longer drain intervals and better fuel economy.

As for the downsides, the only real one is the cost. Depending on your region, synthetic oil will be at least two times costlier compared to regular motor oil.

However, the difference is not as steep as you think – after considering the less frequent oil changes you need with synthetic oil.

Contrary to popular belief, there’s no harm in using synthetic oil in older vehicles.

The earlier synthetic oils were ester-based and would swell the engine seals, resulting in oil leaks. However, synthetic oil companies have reduced the concentration of ester since then, which makes their oil perfectly fine to be used in older vehicles.

Synthetic Blend

At last, we have the synthetic blend. It’s a mixture of conventional and synthetic oils, which gives them the benefit of both.

It offers better protection than conventional oil and is more affordable than full synthetic oil.

On the flip side, however, it’s less effective against engine wear and sludge than full synthetic oil and also requires more frequent oil changes.

Can You Mix Full Synthetic Oil With Synthetic Blend?

Yes, mixing synthetic oil with a synthetic blend is technically possible.

As both have common base oils, using them together will not harm your engine.

That said, I won’t recommend doing so because it’ll not be suitable for the engine’s performance.

Mixing the synthetic blend will reduce the engine performance as the concentration of synthetic oil is now reduced (synthetic blends only contain 10%-50% of full synthetic oil).

That’s especially true if you’ve previously used only the full synthetic oil in your vehicle.

In general, you should only mix the engine oils if there’s an emergency or your preferred oil is unavailable.

Frequently Asked Questions

Can I Mix Two Different Synthetic Oils?

Yes, you can mix synthetic oils from different brands (such as Pennzoil and Castrol) if they have the same viscosity (5W-30 with 5W-30, for example).

Is Full Synthetic Better Than Synthetic Blend?

The full synthetic oil is better than the synthetic blend regarding oil change intervals, fuel economy, and protection against engine sludge. On the other hand, synthetic blend costs less than full synthetic oil and still performs better than conventional motor oil.

What are The Disadvantages of Synthetic Blends?

Compared to conventional oil, synthetic blends’ main disadvantages are higher costs and less compatibility with older engines.

Can You Mix Synthetic Oil With Conventional Oil?

Yes, you can mix synthetic and conventional oils if their viscosity is the same and is recommended by your vehicle manufacturer. However, it will dilute the benefits of synthetic oil and may result in performance degradation.

Is Synthetic Blend the Same as High Mileage Oil?

High-mileage oils are specially manufactured for engines with high mileage, such as over 100,000 miles. These oils often include specific additives designed to condition and protect the seals and gaskets in older engines to prevent leaks. They’re available in many forms, such as conventional oil, synthetic blend, and full synthetic oil.

Andy is an avid car enthusiast with over 5 years of experience in DIYing auto maintenance. He founded AutoProblemz to share his knowledge and expertise with others through writing. His aim is to cut through jargon and help you make the right decisions for your vehicles.

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