Conventional vs Synthetic Oil- Ideal for Diesel Engines

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Good engine oil is always necessary to ensure the engine gets enough lubrication and is not damaged, even during extreme weather conditions. On top of that, the engine oil also helps keep sludge at bay from the narrow passages and increases the engine’s lifespan.

Most car owners probably use the conventional engine lubricant. But there is also another type- synthetic oil. Choosing between traditional and synthetic oil is a tough nut for many car owners with diesel engines.

While conventional engine oil has its benefits, synthetic oil can also be used as it can help to attain the same efficiency as the conventional lubricant.

Interesting, right? Here, we have discussed all the differences between conventional and synthetic engine oil to ensure you can choose the right one for your diesel car engine!

What is Conventional Oil?

It is the traditional and most used engine oil to date. It is made of 100% crude mineral oil refined and distilled multiple times to create heavier petroleum oil, which is used as the base oil. Then, a few additives are added to formulate viscous oil that offers proper lubrication for your diesel car engine. Conventional engine oil is affordable and readily available. You need to change the oil after 3,000 to 5,000 miles of driving. Conventional oil is mainly used for older car models without complicated and advanced engines.

Pros and Cons of Conventional Oil

Pros of the Conventional Oil

  • Affordable: Conventional engine oil is very cheap, and anyone can afford it. The price ranges from $2.8 to $5.5. So even if you are on a tight budget, you can afford it. The cost is slower because the oil is derived from natural crude oil through repeated distillation, a cost-effective manufacturing method.
  • Availability: Conventional oil is also readily available anywhere. You can find it even in gas stations or auto repair shops without worry.
  • It is Ideal for Older Vehicles: If you have an older diesel vehicle (20 years or older) that doesn’t have a complicated advanced engine like a modern car, conventional engine oil can be a great option. Since these car engines were initially designed for conventional oils, they work better with the traditional lubricant.

Cons of Conventional Oil

  • Not Enough Heat and Cold Resistance: Traditional engine oil is not as great as synthetic oil regarding temperature resistance. In freezing weather, the oil becomes more viscous and takes longer to circulate inside the engine, which can cause damage. On the contrary, the scorching and humid weather makes the oil thinner and evaporates faster. Hence, the engine may not get enough lubrication, leading to heat-related damage.
  • Poor Engine Protection: Conventional oils have a higher viscosity and the viscosity changes with temperature change. Hence, it does not offer all-round engine protection, especially during extreme weather conditions.
  • Higher Oil Cost: Conventional engine oil leads to higher expenditure in the long run. Even if the oil is cheaper, you need to spend a lot more to buy more oil bottles, which expands your maintenance cost to a certain extent.
  • Higher Emission: Traditional engine oil does not cut down emissions from the engine. It is because the oil changes with temperature and bonds with the water vapor and contaminants in the air.
  • Poor Fuel Mileage: Traditional engine oil has poor temperature adjustments, forcing the engine to work harder during colder weather.

Hence, the engine burns more fuel, and the fuel mileage decreases, increasing fuel expenditure.

What is Synthetic Oil?

Synthetic engine oil is designed artificially to create a viscous lubricant for diesel engines. It was first introduced in the market in 1929 and used for high-end vehicles like aeroplanes and luxury cars. Germany used it extensively during World War II and was slowly introduced to the world after the world ended.

During the 70s, the American energy crisis led to the introducing synthetic oil as a lubricant for car engines. After 2000, most diesel cars were designed with synthetic oil in mind, and the car you buy has synthetic oil inside its engine as a lubricant. Synthetic oil is mainly used for engines that are advanced and compact.

Synthetic Oil is of Two Types- 100% Synthetic and Semi-Synthetic Motor Oil

  • 100% Synthetic Oil: 100% synthetic engine oil is made from group IV, Group V PAO, or polyalphaolefin base oils and is chemically processed at high temperatures. This type of oil is resistant to temperature drops and lasts longer. It also has different chemically enhanced additives that offer better engine performance.
  • Semi-Synthetic Engine Oil: It is made of Group III PAO oils and traditional engine oils. Hence, this oil offers the benefits of synthetic engine oil but is more affordable than the 100% synthetic engine oil variants.

Pros and Cons of Synthetic Oil

Pros of Synthetic Oil

  • Consistent Performance Even in Drastic Temperature Change: Synthetic oils offer consistent performance throughout the year, even during extreme hot and cold climates. The oils have better heat transference and can resist temperature change as the temperature drops. So, the oil retains its viscosity and keeps the engine healthy even during freezing winters.
  • Consistent Performance: Synthetic engine oils do not change their properties drastically and maintain the ideal condition for a long time. Hence, the engine gets proper lubrication.
  • Long-Lasting: Synthetic engine oils are designed in such a way that it doesn’t break or evaporate quickly. Hence, the oil lasts for a long time without any issues. You just need to change the oil after 10,000 or 12000 miles.
  • Less Polluting: Synthetic lubricants are long-lasting and offer less emission compared to traditional engine oils. It also doesn’t break easily and does not react with water droplets and other contaminants in the air. Hence, the overall emission is less, and it prevents air and environmental pollution to a certain extent.

The Cons of Synthetic Engine Oil

  • Price is Costly: The main con behind synthetic oil is that it is costly. It starts from $6 and goes up to $10 or even more for a one-liter bottle. But, the oil lasts longer compared to traditional engine oil. Hence, it may help to cut down costs in the long run.
  • Not Easily Available: Synthetic motor oils may not be available quickly, especially if you need a particular brand for your diesel car engine. So finding a new bottle can be a challenge sometimes.
  • May Not be Idle for Old or Brand-New Diesel Cars: If your diesel car is very old and has nearly reached its lifespan, switching to synthetic engine oil may not be a good idea. The engine was initially made of conventional oil, and a sudden switch can hamper its performance. But, in this case, switching to semi-synthetic oil can be a good option. On the contrary, using a new brand of synthetic oil can also be a hassle for brand-new cars. Most new car engines have an inevitable friction that must go down gradually. But, synthetic oils may not offer assistance in this matter.
  • Not Ideal for Rotary Engines: Rotary engines that store a part of the engine oil inside their combustion chambers for lubricating the apex seals are incompatible with synthetic oil. The seals may develop sticky and viscous slugs, and it can cause the engine to get more damage.

Conventional and Synthetic Oil- Differences

Let’s check the difference between conventional oil and synthetic oil for diesel engines-

1. Performance

If you check performance, the synthetic oil fares better as it does not get volatile like the conventional engine oil during extreme cold or hot temperatures. In other words, synthetic oil maintains its viscosity better and provides all-round protection.

But that does not mean the traditional oil does not work at all. It may be a deal for less complicated diesel engines that are too compact.

2. Affordability

If you check out affordability, both fare similarly in the long run. Traditional engine oil is cheaper, but you must change oil after the 3000-5000 miles run to add it when the temperature changes. Hence, you end up spending more volume of engine oil, leading to a higher cost in the long run.

On the contrary, synthetic engine oil seems expensive. The oil lasts longer, and you only need to change after driving the car for 10,000 miles; in the long run, you spend more or less exactly the same amount you spend in the case of conventional engine oil.

But, for many people, switching to a $6-$10 synthetic oil bottle may be more difficult than using $3-$5 conventional engine oil. In this case, you can switch to semi-synthetic oil.

3. Availability

Traditional engine oil is available in most places, and you can find it even in a remote gas station shop. So, changing oil may be a bit easier any time. But, for synthetic oil, you must visit a standard auto repair shop, which makes oil change difficult if you need help finding the right brand. But more shops are now selling branded synthetic oils.

How Often Should I Change My Motor Oil?

Well, it depends on multiple factors like the engine oil you use, the road you drive on, the car models, etc. Let’s check some recommendations by experts-

a. Change Once in Six Months or After Driving 3000 Miles

  • Changing oil once after six months or after driving 3000 miles or 3000-5000 km is enough. If you use conventional engine oil, if you have a car that is an older model, changing oil after 3000-5000 km is recommended.
  • For newer models with conventional engine oil, change the lubricant once after driving 5000-7500 miles or 8000-12000 kilometres. Most car manufacturers recommend this frequency, and it is also globally common.
  • Even if you do not drive frequently and do not make long road trips, you should change the car oil at least twice a year or after six months. It helps to retain the health and performance of your car engine.

b. Change After 10,000 Miles.

  • If your car runs on synthetic oil, you need to change the oil less frequently. Changing the synthetic oil once after 10000-1200 miles is enough as the synthetic oil is long-lasting.

How to Determine Which Type of Oil is Better for Your Vehicle?

You need to check the manual of the car manufacturer to determine the type of engine oil if it mentions, you know which type of oil you need.

If you are driving a new car, go for premium-grade conventional engine oil, which allows the new engine to break its resistance and helps the car engine attain the proper state as you start driving.

Synthetic oil is best if you use a heavy-duty car or a heavy–duty diesel vehicle like a trick, a bus, or a minivan. Similarly, newer cars with compact and complicated engines also need synthetic oils.

Suppose you need extra protection as you drive your car on different roads and in different conditions. In that case, you can switch to semi-synthetic engine oil that offers excellent protection and the benefits of both worlds.

Which to Choose, Conventional or Synthetic oil?

Even though the synthetic engine oil performs better and is more stable, you must choose depending on the car model. Synthetic oil is always a bit better than conventional oil. If your car is incompatible with 1005 synthetic engine oil, you can always switch to semi-synthetic blend oil.

You can talk to an automobile expert to choose the right oil for your car engine.

Is Synthetic Oil Better for Diesel Engines?

Yes, synthetic oil can be better for diesel engines if you choose the suitable variation- the semi-synthetic or the 100% synthetic, depending on the car model. Most new car models are compatible with 100% synthetic motor oils; manufacturers also recommend using that.

Similarly, if you travel on long road trips or in extreme cold or hot temperatures, switching to synthetic engine oil can offer some extra protection to your car engine.

Conventional vs Synthetic Oil – FAQs

1. Should I change from conventional oil to synthetic?

Ans: Synthetic oils are more stable and work well even during freezing winter or scorching summer. On top of that, these types of engine oils prevent sledges from blocking your engine. Hence, these oils can help if your car supports synthetic engine oil.

2. Does conventional oil last longer than synthetic?

Ans: No, conventional oils do not last longer than synthetic oils. Traditional engine oils are made of crude petroleum oil, and their viscosity changes as the temperature changes. On the other hand, synthetic oils are made of purely processed materials that do not lose their viscosity even during temperature changes.

3. How often do you change synthetic oil?

Ans: Experts recommend that you need to change synthetic oil every 7,500 – 15,000 miles.

4. Is synthetic oil necessary for daily commuters who drive short distances?

Ans: Synthetic oil can be equally beneficial for daily commuters who drive short distances because it offers better protection when the engine starts and prevents engine damage.

5. What happens if you change the oil but not the filter?

Ans: An oil filter keeps the oil clean from sludge and impurities and helps to regulate the oil flow inside the car engine. So, if you do not change the filter, the engine may get contaminated, leading to engine damage or even complete failure.

6. Does using synthetic oil require a different oil filter?

Ans: Synthetic oil does not need any different filter, and you must choose a high-quality filter compatible with the oil you are using to get maximum benefits.


While traditional engine oil is made from distilled crude oil, synthetic oil is made from processed PAO chemicals. There is also another variation of semi-synthetic oil, which bleeds conventional oil and synthetic oil to get the benefits of both types.

Older engines may be compatible with conventional engine oil. But that doesn’t mean you can switch to synthetic oil. Synthetic oil is less volatile, stays longer, prevents large buildings, and needs to be changed less frequently than conventional engine oil. Newer and premium cars mostly need synthetic oils to keep their engines running smoothly.

But, it is always advisable to research and discuss with an expert if you switch from conventional to synthetic. Switching to semi-synthetic engine oil can also help older diesel engines to get more benefits in the long run.

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