The role of the base oil and additives in engine oils

Without going too deep into the details, engine oil can be described as a blend of base oil and additives. Depending on how the base is obtained, industrial oils can be split into mineral, synthetic and semi-synthetic. The base for mineral oils comes from crude oil and petroleum products, while synthetic bases are produced through chemical synthesis. In semi-synthetic oils, mineral and synthetic bases are blended in varying proportions.

On its own, a base oil has a number of important performance properties, but it can't be used without various additives being blended in. It's precisely the additives that make it possible to account for the design features and operating regime of each particular engine. Additives are put into engine oils to weaken, strengthen or stabilise certain properties the oil already has, and also to give it new properties needed for the engine to run properly.

The additives blended into engine oil during manufacturing perform an extremely wide range of jobs — from stabilising viscosity at particular temperatures to cleaning the engine's internal components. Manufacturers don't disclose the composition and properties of their additives, guarding them as trade secrets. For the average consumer, the exact composition doesn't matter. What does matter is whether the additive package in a given brand of oil meets global standards and the additional requirements automakers set for oil composition.

So it's precisely the balanced additive package contained in any given engine oil that makes it suitable for use in a particular engine. In other words, the sheer variety of engine oils exists because of the sheer variety of engines, built for different purposes, by different manufacturers. For example, some engines are designed for sports cars, others for towing trailers, and others still for mountainous terrain, and so on.

Automakers build quite specific future operating conditions for each engine into the technical specifications right from the start. The designers' task then comes down to optimising the engine's construction as much as possible for the given conditions.

The choice of engine oil is shaped by a whole range of requirements driven by the engine's displacement, its design, and the specific materials its components are made from. Because of this, some engine oil parameters can be mutually exclusive across different engines. Using an oil that doesn't meet these requirements leads, at best, to accelerated wear of engine components, and at worst puts your life at risk!