There are two main types of base oil: mineral and fully synthetic. Motor oils labelled as ‘part-’ or ‘semi-synthetic’ or ‘synthetic technology’ contain a mixture of these two types.

Mineral base oils come from crude oil that is processed in a refinery to separate out the fractions with useful lubrication properties and remove unwanted components such as waxes. Unlike some motor oil manufacturers, Shell makes its own top-class mineral base oils by selecting the best crudes and employing stringent quality control procedures throughout the entire production process.

Synthetic base oils give enhanced performance because they are manufactured using a more expensive chemical process than that used in mineral oil production. Because of this, fully synthetic oils like Shell Helix Ultra flow more easily at start-up temperatures, when most wear occurs. They are also more resistant to heat and are more easily protected by antioxidant additives (oxidation is a natural degradation process that occurs in oil over time). Plus they are less volatile than mineral oils.