Can You Use Conventional Oil After Using Synthetic? The Answer!

Synthetic oil and regular oil have the effect of lubricating the engines in the vehicle, preventing wear and tear. However, most people do not fully understand the difference between synthetic and regular oil. There are many cases where car owners prefer to use synthetic oil because of its superior features when compared to regular oil.

However, after a while, they feel that synthetic oil is quite expensive. It is difficult to find a fully synthetic oil with 100% of purity, so they want to switch to regular oil. One question that arises from such cases is “Can you use regular oil after synthetic oil?” We will shed some light on this question; also, we’ll learn more about regular and synthetic oil later, and the pros and cons of both.

What Is Synthetic Oil?

Synthetic oil is a lubricant consisting of man-made chemical compounds. Synthetic oil can be produced using chemically modified oil components instead of whole crude oil, but can also be synthesized from other raw materials.

However, the base material is still overwhelming crude oil that is distilled and then physically and chemically modified. The actual synthesis and composition of additives is generally a trade secret and will vary between manufacturers.

The molecular homogeneity will greatly reduce the friction when the synthetic oil collides with each other and limit the heat generated. It is also much more stable in-state than mineral oil at various temperatures. In other words, synthetic oil doesn’t thin out excessively when heated or solidify at low temperatures.

Maintaining viscosity and limiting molecular evaporation will avoid direct metal collisions when the engine is running – minimizing wear and tear. In addition, being well-lubricated also helps the engine start easier, minimizes wear on machine parts (which is often the heaviest in the detonation phase), and reduces the load on the battery.

Finally, synthetic oil will also help manufacturers to reduce the volume in the engine – a move that allows for reduced vehicle weight, cost savings, and environmental protection.

Pouring oil to car engine.

Besides the full synthetic oil we often know, some manufacturers also offer semi-synthetic oil (Semi-Synthetic or Synthetic Blend – Synthetic Technology). With a formulation of no more than 30% fully synthetic oil and a lower price tag, of course, this oil is not as good in engine protection as fully synthetic oil; but is very suitable in terms of price and performance ratio results for many users.

Synthetic oil is not new to the car world. As early as 1920, the first products of this group began to appear on the market. By World War II, when the Allies blocked oil supplies to Nazi Germany, the country’s synthetic oil technology entered a period of great development.

By the 1950s and 1960s, the rapid development of aircraft increased the demand for oil with superior properties that were not available with regular oil. By 1970, when the energy crisis hit, Mobil took the opportunity to introduce synthetic oil products with the promise of making cars more energy efficient.

Today, along with cars with “terrible” performance or small engines to optimize performance (or even add turbochargers), the demand for lubricants with outstanding efficiency and certain must-have attributes becomes even more imperative. This makes synthetic oil technologies also develop at a rapid rate.

Pros and Cons


1.     Superior thermal stability of synthetic oil

One of the greatest benefits of synthetic oils comes from their molecular stability. Because regular oil is a mixture of many impurities, it is usually composed of molecules of different lengths consisting of small, medium, and long hydrocarbon chains – unlike synthetic oil, which only has molecules of medium size.

As such, short hydrocarbon molecules with a lightweight often burn when heated, causing the synthetic oil to thicken after a period of time in the engine (which can lead to clogged oil pipes or reduce the amount of oil “evaporating” – this is very important for engines with turbochargers).

2.     Longer life for the engine when using synthetic oils

With synthetic oil, besides being more resistant to temperatures than conventional oils, also carry heat better and is less prone to evaporation – keeping engines running cooler and more durable.

Even though they are more expensive, synthetic oil has a shelf life of 3-4 times longer than mineral oils – not to mention the other benefits during that time.

In fact, also because of its less prone to oxidation and degradation, synthetic oil can be used for a much longer time than mineral-based oil, which degrades quite quickly. This means users can replace them every 15,000 – 20,000 km – which is 3 to 4 times the cycle of regular oil (under standard operating conditions).

This is a huge advantage when you take into account its convenience and role in long journeys as well as the safety of the natural environment. In this respect, a higher price tag than mineral oil would be perfectly justified – if not still cheap.

Car fuel gauge.

3.     Synthetic oil is more fuel-efficient for engine

Besides extended oil change intervals, synthetic oils also offer many other obvious benefits.

According to Pete Misangyi – director of Ford’s petroleum and lubricants division, the company’s experts recently decided to switch to using the default 5W-30 oil, 5W-40 with lighter weight to help the car save fuel economy.

Lighter oil will allow them to be pumped more easily – which means less energy to run the pump. In fact, high-grade synthetic lubricants can help save fuel costs from 2% to 4%.

Even Ford uses a variable oil pump that allows less oil to flow when the engine is running at low power. Along with a number of other improvements, the American automaker now recommends that users change the oil at a threshold of up to 20,000 km to reduce maintenance costs and save more time.

4.     Synthetic oil can be used for all types of engines

In the face of mixed opinions about the negative effects of synthetic oils, most experts disagree with statements such as a car using regular oil for too long, or an old car, a car with a large number of kilometers should not be converted to synthetic oil.

That way, all cars today can benefit from synthetic oil – whether it’s used, new, entry-level, or expensive high-performance vehicles.


1.     Synthetic oil is very expensive, 2 – 4 times more than regular oil

It is not recommended to use synthetic oil for new cars. New cars need the friction created when they regularly use oil to operate efficiently.

A man holding a canister of motor oil.

2.     Hard to find

Finding 100% synthetic oil is very difficult. Most of the synthetic oils on the market today are mixed, not 100% pure.

What Is Regular Oil?

Regular oil or conventional mineral oil is a product distilled from mazut and goudron residues – which are extracted from fossil sources. This crude oil is picked up from the ground and refined through several steps to remove impurities. It is then mixed with many other chemicals (additives) before being available to retail consumers.

Regular oil has mineral base oil as the main component, which can account for 85% to 100% of the finished oil by weight and has a major role in the performance of the lubricant. Most regular oil is made from crude oil, a mixture of hydrocarbon molecules with heterogeneous shapes, sizes, and physicochemical properties.

Hence, when using regular oil, the lubricating performance of the engine is not stable, especially in conditions where the temperature is too low or too high. Because of the above disadvantages of this type of oil, consumers are gradually switching to using semi-synthetic oil and synthetic oil instead of regular oil.

Pros and Cons


1.     Low cost

Simple distillation technology, and easy-to-find materials, lead regular oil to the cheapest price among lubricating oils. Regular oil is suitable for low-income people.

2.     Ideal for new vehicles

Most manufacturers use conventional oils in the assembly process of their vehicles. Vehicle owners should use regular oil for new cars. A new car needs to go the first 5,000 miles with regular oil for the process to work more efficiently.

Old model car cruising the highway.

3.     Suitable for old cars

You can use regular oil for old cars from the 2000s and earlier. Since these cars cannot take advantage of the benefits of synthetic oils, conventional oils would be the best idea for them.

4.     Easy to buy

You can easily find regular oils at your local stores. That means you can buy them whenever you want.


1.     Low Stability

Most mineral oils are derived from crude oil, a mixture of hydrocarbon molecules with heterogeneous physicochemical properties, sizes, and shapes. Therefore, the lubricating performance of regular oil is not stable, especially under conditions of extremely low or high temperature.

2.     There are many impurities in regular oils

On the other hand, petroleum experts must also admit that there is no absolute way to remove all insoluble substances such as paraffin, wax, silicone, soil, etc.

Therefore, during operation, these impurities will form deposits in the engine. These residues over time will make the lubricating oil worse, your car will quickly heat up, thereby degrading faster.

Car brake down due to engine overheat.

3.     Short lifespan

Conventional oils have a higher breakdown rate, so their lifespan is shorter. So you will have to change constantly to protect engine parts.

Can You Use Regular Oil After Synthetic Oil?

The application of regular oil and synthetic oil is the same, so you can completely use regular oil after using synthetic oil. Some myths say that once you use synthetic oil, you can’t use regular oil after that.

That is the wrong advice. The truth is, these are two different oils, but the application on the car and the engine are the same. They all function as a lubricant to keep your vehicle’s engine performance stable and smooth.

Some people worry about what will happen when they use regular oil after using synthetic oil. Changing the synthetic oil to regular oil will not affect the vehicle’s performance.

However, there will be some changes in the stable performance of the engine. When using synthetic oil, the engine will be much more stable. Experts also recommend that you use synthetic oil rather than regular oil. Synthetic oil will help you increase the life of your car.

If you intend to convert synthetic oil to conventional oil, you should consider a number of factors. It is better to gradually introduce a completely new engine oil. You can switch to synthetic at first, and then convert to regular oil for your vehicle. When changing the oil type, you should also change the oil filter manually.

Before making this change, consider the condition of your vehicle. It will be easier with new cars when you intend to switch oil. But, with old cars, it’s completely the opposite. Older vehicles can have some leakage problems when you switch from one oil to another. Therefore, you can consult the vehicle manufacturer before changing the oil.

Regular Oil vs Synthetic Oil

Synthetic oil is a synthetic lubricant containing a more refined base oil than the base oils used in regular oil, providing perfect protection and maximum performance. Synthetic engine oil provides many benefits that keep engines running at optimum performance for many years.

To understand synthetic oil, let’s look at the origins of motor oil.

There are two basic types of lubricants available today:

  • Conventional mineral oil is the traditional and still most widely used type.
  • Synthetic lubricants are increasingly popular.

Both are made from crude oil in the ground. The difference is that synthetic oil is made from a more advanced refining process, and is of higher purity and quality than regular mineral oils.

Not only does this remove any impurities from the crude oil, but it also allows the individual molecules in the oil to be uniformly tuned to suit the needs of modern engines. These homogeneous molecules provide a higher level of protection and performance.

The performance characteristics of synthetic oil are stronger, especially in terms of low-temperature and high-temperature stability, and protection against deposits. These properties result in less engine wear, increased fuel economy, and longer engine life.

Synthetic oils have been specially developed to adapt to the harsh conditions found in modern engines. They have a freer flow than conventional oils. The biggest benefit is enhanced engine protection.

When an engine starts, regular oil takes a long time to circulate, which creates friction between unlubricated parts and wear. In contrast, synthetic engine oils circulate faster at start-up, protecting the moving parts inside the engine.

Synthetic oil can also significantly improve fuel economy. During the warm-up phase of a car journey, regular oil is denser and moves slower, making the engine drier and less efficient. Because synthetic oil can work faster, the engine will reach peak performance much sooner.

Another advantage of synthetic oils is that they are cleaner and more environmentally friendly – helping to reduce engine emissions compared to conventional oil. Regular oils also contain many impurities such as unsaturated hydrocarbons, sulfur, and other undesirable impurities that cannot be completely removed by conventional crude oil refining.

In all these important respects, synthetic oil outperforms regular oils. Synthetic oil brought significant benefits compared to motor oil normally, such as:

  • Protection formidable
  • Minimizing the degradation
  • Lubricant faster startup at low temperatures
  • Protection superior high temperature
  • Exceptionally resistant to thermal oil breakdown
  • Cleans the engine
  • Protects against harmful deposits
  • Increases engine efficiency
  • Increases oil oxidation resistance (condensation) reduces engine traction
  • Low oil consumption more efficient under high-speed conditions
  • More efficient engine operation over a wider range of temperatures

However, synthetic oils are too expensive to obtain, and fully synthetic oils are also difficult to obtain. Therefore, in some cases, synthetic oil is not necessarily more suitable than conventional oil.

Although regular oil has many weaknesses when compared to synthetic oil, the quality of a final product is not only by oil and oil’s original decision. Some cheap synthetic oil often uses poor quality additives (eg. friction modifiers, antioxidants, detergents, types of antifreeze) that cause them to disintegrate so fast during engine operation.

In other words, mineral oil with a good formula and good quality is still worth using rather than a cheap synthetic oil with a bad formula. And so, don’t try to find synthetic oils with “suspicious” cheap prices.

It’s perfectly fine to use good quality mineral oils in popular cars – as long as the replacement period is indicated. However, with high-performance vehicles, fully synthetic oil is almost a must. Either way “follow manufacturer’s instructions” remains the ultimate criterion that anyone should adhere to.


Synthetic oil has many benefits over conventional oils because of better lubrication, which helps prolong engine life. Synthetic oil is an ideal choice for expensive cars, luxury motors with high performance

However, you can absolutely exchange the use of synthetic oil for regular oil. There will be some difference in engine performance when you use regular oil. So, before making a decision, consider what type of vehicle you have, and consult the manufacturer.

At the same time, you should change it regularly during using regular oil. It will help the car engine run smoothly and minimize damage.

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About Matthew Webb

Hi, I am Matthew! I am a dedicated car nerd! During the day, I am a journalist, at night I enjoy working on my 2 project cars. I have been a car nerd all my life, and am excited to share my knowledge with you!

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