Engine, or motor, oil is designed to lubricate the inner components of internal combustion engines, as well as to protect them against corrosion and keep them cool while in use.
It’s made from two main elements: base stock and additives. The base stock commonly makes up 95 per cent of the solution and is either made from petroleum, synthetic chemicals or a mixture of the two. The base stock is responsible for lubricating an engine’s moving parts and removing built-up heat. The additives, meanwhile, account for roughly five per cent of the oil and it is these chemicals that are responsible for finely controlling oil viscosity and lubricity, as well as protecting engine parts against wear. For example, zinc dialkyldithiophosphate (ZDDP) is a frequently used additive for preventing wear, while magnesium sulphonates help the oil to break down impurities and engine sludge.
Engine oils are rated by their grade and viscosity. Any oil can either be single-grade, with a set viscosity level, or multi-grade in which the oil can act at two different viscosities depending on its temperature. The latter is most prevalent today, to cater for vehicles used all year round in various conditions. The flow-rate of both single- and multi-grade oils is measured on a viscosity grade scale, which includes 11 grades ranging from 0 to 60. Lower-ranked oils are thicker than higher-ranked ones, making them more suitable to hot environments, and vice versa.