Why synthetic is better than ‘natural’

Natural products are traditionally considered to be ‘better’ than synthetic ones. In the case of engine oil, however, Shell scientists have succeeded in developing a range of synthetic products with better properties than their natural counterparts – and fewer of their shortcomings.

Synthetic base oils give enhanced performance because they are manufactured using advanced chemical processes, so their molecular structure and hence, their properties, can be closely controlled. For example, fully synthetic oils like Shell Helix Ultra are designed to flow more easily at start-up temperatures (which is when most wear occurs). They are more resistant to heat and more easily protected by antioxidant additives (oxidation is a natural degradation process that occurs in oil over time). They are also less volatile than mineral oils.

For example, compared with a normal API SG/CD mineral oil, a fully synthetic engine oil such as Shell Helix Ultra is found to deliver:

  • Up to five times better cleansing.
  • Up to three times more protection.
  • Less than half as much engine wear.


Key advantages of synthetic engine oils include:

  • Higher purity and quality than mineral base oils – which means fewer unwanted components including sulphur-containing compounds and reactive or unstable hydrocarbons.
  • More uniform and consistent molecular composition – which reduces the fluid friction levels.
  • Can be reliably tailored to meet the requirements of modern engine manufacturers (requirements that oils like Shell Helix Ultra don’t just meet but often exceed).
  • Shell Helix synthetic oils are designed to perform under the more extreme conditions encountered in modern engines.
Why do synthetic oils perform so well?
Properties of synthetic oils Resulting benefits
Low overall viscosity and reduced friction in the fluid means superior flow properties. This results in improved engine efficiency and fuel economy, and lower oil temperatures.
Thanks to the oil’s high viscosity index, the viscosity is affected less by temperature changes than with normal mineral oils.

The oil does not become too thick when cold, or too thin when hot. This reduces engine wear at temperature extremes.

Less viscosity modifier is needed, which leads to lower levels of deposits.

In high temperatures, viscosity and shear resistance are retained. This means better engine protection at high speeds or when heavily loaded.
In low temperatures, oils do not thicken unduly. This means easier starting with less strain on the battery. Oil circulates quickly around the engine, giving protection from the outset. The engine warms up faster and reaches optimum performance sooner, which improves fuel economy.
Low volatility means fewer volatile components in the oil and so less evaporation or burn-off. This results in lower oil consumption, fewer top-ups and less oil thickening, which helps to maintain fuel economy and reduce engine wear.
High oxidation resistance means that the oil molecules are less likely to breakdown or degrade, especially at higher temperatures. This keeps the engine cleaner through reduced formation of sludge and corrosive acids, fewer engine deposits and less oil thickening – all helping to maintain fuel economy and reduce engine wear.