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Synthetic Oil vs. Regular Oil

Test tubed with Synthetic Motor Oil

Is Synthetic Motor Oil Best For Your Car?

Synthetic motor oils have been marketed and recommended for many years and are well recognized as delivering better performance vs. conventional oils. What’s the difference between synthetic and conventional oil? Synthetic motor oils are better in the following key areas:

  • Provide improved protection from high levels of engine heat delivering better thermal stability. This enhances the motor oil ability to resist thermal breakdown.
  • Deliver better protection from oil burn off or evaporation loss/volatility. This helps to improve oil consumption control.
  • Enable greater deposit control protection improving engine cleanliness   
  • Can provide enhanced viscosity control to better resist engine shear forces and help prevent viscosity grade breakdown
  • Enable the formulation of motor oils that offer better low temperature performance. This includes better low temperature pumpability, start ability and oil flow.


Synthetic motor oils can also offer improved protection when operating vehicles under high stress and load such as towing, hill climbing, and quick accelerations. In turn, a synthetic motor has many advantages over conventional oils and is better in performance in many areas compared to regular motor oil.  This is why every engine will benefit from a full synthetic motor oil whether required through the manufacturer’s specification or not. 

What Is Full Synthetic Motor Oil?

Today motor oils are classified as full synthetics or part synthetics. In a full synthetic motor oil, the entire base oil content is comprised of hydrocarbons that have been transformed or synthesized into new stronger molecules.  This is different than regular motor oil which utilizes base oil that are more dependent on the properties of the crude oil used to produce regular mineral base oils. For a part synthetic blend, the base oil in the motor oil contains a combination of synthetic and conventional base oil components. With this part synthetic oils can provide enhanced performance somewhere between conventional and full synthetics.


Today, many vehicle manufacturers are specifying motor oils that require synthetic formulations. European Manufacturers have long specified oils that are full synthetic. In addition, by recommending approved dexos fluids General Motors are requiring synthetic technology motor oils. Lastly as vehicle manufacturers strive to deliver higher level of fuel economy and lower carbon dioxide emissions, lighter oils have been introduced into the marketplace such as SAE 0W-20 and in select applications SAE 0W-16. Such lighter grade oils require the use of synthetics to achieve the low temperature oil flow requirements of the 0W grade, and to ensure oil volatility or burn off is controlled when using lighter viscosity base oils.


 Full synthetic motor oil, being higher in performance than conventional oil, will generally provide better protection should an oil drain interval be inadvertently extended beyond the manufacturer recommendation.  This said, unless extended service has been demonstrated and claimed, Castrol advises that motorists always follow the manufacturers’ recommendations for oil specification and grade as well as oil change interval. Use the following guide from Castrol to explore all available motor oil types.

Chemist working on Synthetic Motor Oil