Engine oil: Synthetic oil vs conventional oil

In our previous article we saw that modern synthetic oil is better than conventional oil because of its multigrade ability among other things. This allows the oil to change its viscosity nature instead of needing additives. Aside from that, what are their differences?

Conventional oil

Also called regular or mineral-based, its base are hydrocarbons from petroleum. The popular thinking is that this is bad, but it does have its advantages.

The main advantage is obviously the price. It is not quite expensive because it derives from from abundant raw materials. As it is not created, the price reflects a lower cost.

Also, thanks to the nature of the petroleum, it has a tendency to be monograde, which has lots of potential uses. This property forces the manufacturers to use additives to make these oils suitable for use at more extreme temperatures.

Other common reasoning is that conventional oil, since it has faster degradation, should be changed more regularly. This is both true and false at the same time. Although it has a faster degradation through oxidation, the same specifications and standards apply for both conventional and synthetic oil. So if a conventional oil meets a specification, it should last just as long as the a synthetic oil with the same specification. Therefore, the same cars can use both oils. If you want to read more about oil specifications, remember to check our article about them.

This also means that the time interval to change the oil must be the same for both kind of oils. Always the amount of time or km the manufacturer recommends.

Petroleum pump, source of conventional oil

Synthetic oil

Besides its ability for naturally changing its viscosity depending on the temperature, synthetic oil has some other advantages.

The most important one is that there is virtually no degradation with synthetic oil. This results in a healthier oil lifespan and also ensures the absence of deposits or sludge in the system. This translates into much greater protection against engine wear during its life cycle.

Also, even when mineral-based oils contain additives to improve their viscosity index, synthetic oils still perform better at extreme temperatures. It has better natural protection against thermal breakdown and evaporation at higher temperatures, while retaining its fluidity in low-temperatures climates. That's why lower temperatures oils like 0W20 or 5W30 are usually synthetic.

To sum up, synthetic oil:

  • Performs better in extreme (higher or cooler) temperatures
  • Keeps your engine cleaner from sludge or deposits, which can reduce power, performance or fuel economy
  • Offers greater protection against engine wear

Semi synthetic oil

As the name suggests, semi synthetic oil is a blend of the two previous mentioned base oils. It is also known as hybrid oil.

Semi synthetic oil incorporates the benefits of synthetic oils without the disadvantages of conventional oils. This means that it preserves its good behavior at extreme temperatures but it's not that resilient. Usually higher grade oils like 10W50 or 15W40, event the best, are hybrid or conventional since with proper maintenance there is no real difference to using 100% synthetic oils.

The difference between semi and fully synthetic oil can also be noticeable in the price tag - the semi synthetic oil is generally a little bit cheaper.

For a responsible owner who changes its oil when appropriate, the difference should be almost imperceptible in terms of security, performance at extreme temperatures or wear.

Stay tuned!

In the coming weeks we will talk about how additives (solid or liquid) can improve a motor oil's performance.

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