~An engine in movement undergoes brutal shocks, an extreme heat, high pressure and sharp friction. To ensure the survival of its mechanical components, it is necessary to provide it with adequate lubrication and efficient heat evacuation. For this we use lubricants for engine which are used to lubricate, cool and clean the parts of the engine by the deposit of a protective film between the moving parts of the engine to avoid metal/metal friction. These lubricants are obtained by mixture of a mineral basic oil of petroleum origin (from 80 to 88 %) with a package of various additives (from 12 to 20%). A mineral oil is characterized by rheological properties: viscosity, the viscosity index (VI), the flow point; surface properties: detergency and dispersion and thermal and inflammability properties. These properties can be improved by the package of additives, this last one improves the oxidation resistance, lowers the flow point, raises the VI, contributes to the cleanliness of the engine and ensures a protection against erosion and corrosion. Nevertheless, the presence of the additives in great quantity is harmful, for this we want to minimize the concentration of these additives and at the same time guarantee the correct functioning of the engine.