- improvement of engine start parameters;
- reduction of weight and size;
- increase of power output per liter (power to volume ratio);
- reliability and economy.
To ensure reliable engine operation, it is recommended to use oil with shallow viscosity-temperature curve. The viscosity of such oil shows little change with temperature, therefore they ensure reliable operation in various operating conditions.
Oils with higher viscosity minimize part wear. However, there is a limit to oil viscosity, as exceedingly thick oil causes increased fuel consumption.
To increase power to volume ratio, the compression rate is increased, fuel/air mixture is optimized or air charge boost is used. The operating conditions of oil become harsher, its oxidation rate increases, forming carbonic sediment and varnish. The performance of motor oil degrades. It is not possible to completely recover the oil. However, there are plants available to regenerate turbine, industrial and transformer oils. A good example is the UVR-450/16K made by GlobeCore. The main advantage of this plant is its versatility. The UVR-450/16K can be used for regeneration and restoration of various oil types; it can also purify and remove aromatic compounds from any petrochemical products.
In order to decrease motor weight, lubrication systems are made smaller. This can also lead to intensive oxidation of oil: the smaller amount of oil is circulated more intensively. To decrease the rate of carbon and varnish formation, the oil must possess sufficient anti-oxidation and dispersion properties.
To make engine operation reliable, oils with good anti-oxidation and anti-galling properties should be used.
Besides, the oil must have neutralization properties to decrease the corrosion of parts caused by fuel combustion products.
Motor oils in the market today must preserve the above mentioned properties for a long time (500 – 2000 hours of motor operation, that is, 12 – 45 thousand kilometers of mileage).
Oil replacement schedule must be coordinated with filter replacement and automobile maintenance.
Significant differences between operating conditions in various types and designs of engines make oil selection difficult. A special classification has been developed, with consideration of operating conditions and engine specifications, to simplify this process.