What is Synthetic Oil and How Long Does It Last?

We all know that the fuel (gasoline or diesel) powers the vehicle engine through a process of internal combustion.

Once powered, the engine parts move in coordination so that the vehicle will work. These parts, to operate smoothly requires a lubricant.

The lubricant can be synthetic or conventional which reduces the friction between the parts and favors a smooth operation.

Synthetic oils are superior over traditional oils due to their excellent properties and additives. Let’s know what is synthetic oil and how long does it last.

What Is Synthetic Oil?


Synthetic oil is a lubricant which is used in the automobile industry. Ideal synthetic oil should lubricate the engine parts at various temperatures and offer superior protection for an extended period.

Motor oils are classified depending on the base oil they are made off. Usually, there are five classes/groups of oils based on American Petroleum Institute gravity (API) index.

API Class I and II: Made by using petroleum-based oils. These oils are conventional oils.

API Class III, IV and V: Called as synthetic oils which contain artificial or synthetic oils along with additives.

Both conventional and synthetic oils can be used as lubricants, but over the period, the additives used in conventional oils are destroyed (due to heat fluctuations) and failed to perform their action effectively.

Synthetic oils have a fair amount of lifespan, and the additives used in them make the oil thick at low temperature and thin at high temperatures allowing a smooth flow. The base of the synthetic oil itself is chemically engineered to withstand these changes.

The synthetic oil contains synthetic compounds called as primarily Poly Alpha Olefins (PAO) and esters. These compounds have similar properties of crude oil but do not negatively impact the function (as crude oil does).

Class III synthetic oil is an exception as it has a petroleum base. But the crude oil is highly modified by breaking the multiple hydrocarbon links into simpler and smaller ones who have uniform properties.

API class III oils are considered synthetic in the United States.

There is another group called semi-synthetic oils which is a combination of mineral oil and synthetic oil. The resulting mixture has higher benefits than full synthetic oil.

How Synthetic Oil Is Made?

The word synthetic implies that it is made artificially. But any artificial product must require a primary component so does the synthetic oil.

The base product of a synthetic oil differs for different manufacturers. Many use crude oil while some use natural gas (Pennzoil).

The synthetic oil is a refined product of crude oil which has lesser number of impurities. It involves a series of chemical processing which removes impurities through every step. This chemical process is called the Fisher-Tropsch process.

The crude oil is mixed with other compounds such as methane (CH4) and oxides of carbon (CO, CO2). Then they are combined with other artificial compounds which break the large hydrocarbon chains in the crude oil to smaller and uniform chains.

On the other hand, Pennzoil is made with natural gas as the base through a process called gas to oil process (GTL).

Since natural gas has a lesser number of impurities compared to crude oil, the synthetic oil prepared from natural gas also has fewer impurities.

Uniform size and shape is an ideal property of a lubricant. Other additives such as anti-rust, anti-oxidative agents are added to the synthetic oil to enhance the performance. Viscosity enhancing additives are commonly used in all synthetic oils.

A seal conditioner is also added to retain the elasticity of the oil. Other additives include antioxidants, anti-foam, and de-emulsifying agents.

The viscosity of the oil at various temperatures determines its ability to function. Every synthetic oil is assigned a number based on their viscosity in winter and at normal operating temperature. This grading system is formulated by the Society of Automotive Engineers (SAE).

On a commercial synthetic oil label, you will see a number like SAE 5W-30. In this grade, the number before the alphabet W indicates the viscosity at lower temperatures. Lower the viscosity, better the function (at lower temperatures).

The alphabet W stands for Winter. So, the term 5W means the viscosity (5) of the oil in winter (W).

The numeric 30 indicates the oil’s operational temperature. 5W-30 oil is most widely used but it depends on the country you live in and the climatic conditions.

Why Synthetic Oils are Better Than Conventional Oils?

Synthetic Oils vs Conventional Oils

There are obvious reasons why synthetic oil is superior to conventional oil. It has tolerance for temperature fluctuations and resistant to oxidation and. At extremely low temperatures, a lubricant must have low cold cranking properties.

The cold cranking properties of synthetic oil are lesser when compared to conventional oil (1/3rd of conventional oil).

It also has excellent resistance to oxidation. The oxidative ability will determine how long does an oil last. It is measured by a test known as the Turbine Oil Oxidation Stability Test (TOST). Synthetic oils have high TOST value than conventional oils.

The Noack Volatility test is used to determine the volatility of the oils. Synthetic oils have very less volatility (do not evaporate quickly) than conventional oils.

Apart from these properties, synthetic oil has fewer impurities, no sulfur and do not produce any harmful chemicals or gases.

Watch The Video: Is Synthetic Motor Oil Better For Your Car?

How Long Does a Synthetic Oil last?

The lifespan of synthetic oil is relatively longer than conventional oil. While most servicing firms suggest to change it every 3000 or 6000 miles, it isn’t the case.

There are plenty of companies which recommend to change the oil after one year or at least after covering a distance of 10,000 miles.

If you are a frequent traveler or if you use the vehicle very often even for short distances, it is fair enough to change the oil after one year or after reaching the minimum distance.

The lifespan depends usually on the following factors:

  • Viscosity tolerance at various temperatures
  • Oxidation resistance
  • Additives which enhance the function of the oil
  • The oil manufacturer

Some oil manufacturers promise that the oil change is required after 15,000-mile distance (Mobil 1) or 10,000 miles (Elf).

The cost of synthetic oil is higher than conventional oil, but it requires less frequent changes which means you save more bucks than conventional oil. All in all, less frequent changes is the best way considering the lifespan of the synthetic oil.


Synthetic oil is artificially made lubricant which has a long lifespan. Older vehicles may require conventional oils which need frequent replacements. While car-servicing guys may insist you to change the oil every 3000 miles, it is not a good idea.

Synthetic Oils

The primary reason behind this suggestion is either they do it for the commission, or they are unaware of the advancements. You must also consider which type of oil to use to tolerate remarkably lower temperatures.

A 10W-40 oil may not be suitable for users living in subzero temperatures.

Finally, buy a synthetic oil from a reputed company for better lubrication, function, and duration.

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