Motor oil plays an important role in ensuring a long and reliable operation of the engine, therefore, its choice should be approached seriously and responsibly. Today the market offers a huge number of oils from different manufacturers, however, should not rely solely on advertising and the popularity of certain brands. Expensive, high-quality, wrong engine oil much faster will your car engine failure than budget right automake.
In order to make the right choice let's try to understand types and classifications motor oils:

1. Chemical composition motor oils are divided into mineral, synthetic, semi-synthetic.
Mineral oil is obtained by distillation and purification of oil. It contains a large amount of additives, however, quickly loses its properties. Mineral oils are paraffinic, aromatic and naphthenic, they differ in the structure of the hydrocarbons contained in their composition. The best characteristics are naphthenic.
Mineral oil is pretty cheap, but require frequent replacement. Their application is expedient if the vehicle is not subjected to heavy loads.
Synthetic produced by the synthesis of specific chemical compounds, allowing achieved the desired performance properties. "Synthetic" has a number of advantages: high temperature evaporation, high turnover reduces friction, chemical stability, less prefinished and oxidized, long service life. They are much more expensive than the mineral, however, at high loads on the vehicle, their use is justified.
Semi-synthetic oil is a compromise between the "mineral water" and "synthetics", it is a result of mixing of synthetic and petroleum base components. As a result, it is acceptable for the price and has a better performance than mineral.

2. The viscosity classification SAE. The viscosity of motor oils - one of its main characteristics, it directly affects the ease cold start of the engine in the cold. Classification SAE allows three types of oils viscosity: winter, summer, all season.
Winter is designated by the letter "W" after the number: SAE 5W, 10W, 20W, 25W. The number indicates the minimum temperature to which you can safely use it.
Summer oil marked without beeches: SAE 20, 40, 50.
Season is marked by a combination of winter and summer designations: SAE 10W-40.

3. Performance motor oils are often classified by the American and European systems. European - more strict and evaluates more qualities.
The API (American petroleum Institute) distinguishes 2 categories of oils "S" and "C". Category "S" is designed for gasoline engines, and category "C" for diesel. The second letter in the legend defines the quality of the oil, and the closer it is to the end of the alphabet, the higher the quality. Figures in parentheses represent, for engines a year desirable this class. In the end, the marking looks like this: SL (2001), CF (1994). If the label indicates both markings (SJ/CH), the oil suitable for petrol and diesel engines.
Classification ACEA (Association of European car manufacturers) gives a more complete description and pays great attention to the anti-wear properties of oils. For gasoline engines used marking "A" diesel "In" and "E". The figure indicates the quality (the more - the better). A hyphen indicates year of change or approval specifications.