Discover the differences between mineral and synthetic engine oil
By Bardahl • The 5/12/2021 • 5 min reading
As you know, oils come from the distillation and refining of petroleum. All oil bases are mineral. However, mineral oil has some drawbacks: it is less than 85% saturated, meaning that the hydrocarbon fractions in it are of varying sizes.
As a result, the oil adheres to metal less uniformly, and its cold behavior is described as poor: it takes a long time for the oil to flow and lubricate the upper part of the engine. This explains the higher viscosity grades: between 10W and 20W*.
Mineral oil also does not help reduce fuel consumption. Nevertheless, it has the advantage of not being aggressive with seals in older cars and classic cars. This is why mineral oil, like Bardahl XTM, is still used by many enthusiasts of classic vehicles.
**Synthetic Oil = Stable Oil**
Synthetic oils undergo a more advanced transformation process. The more synthetic the oil, the greater the transformation (addition of synthetic compounds). To achieve saturation, the oils are hydrocracked. In this process, heavy hydrocarbon fractions are transformed into lighter cuts to obtain a more homogeneous and stable oil (see the diagram above). This allows them to flow more easily when cold, hence the lower viscosity (down to 0W for the most modern engines), and also reduces consumption.
The best bases for achieving 100% synthetic oil are composed of PAO (polyalphaolefins, category IV) and Esters.
In summary, although older engines may not accept it (technology and materials used in the 20th century were not the same as today!), 100% synthetic oil has only advantages: better high-temperature resistance, reduced consumption, better lubrication, and therefore, better protection. Additionally, synthetic oils prevent oxidation.
To be completely thorough, remember that an engine oil is nothing without additives (5 to 50% of its composition). Find more information about additives here.
*Understand engine oil language with Bardahl:
https://bardahl.fr/fr-fr/nos-conseils/comprendre-le-langage-des-huiles-moteur