Most motor oils are made from a heavier, thicker petroleum hydrocarbon base stock derived from crude oil, with additives to improve certain properties. The bulk of a typical motor oil consists of hydrocarbons with between 18 and 34 carbon atoms per molecule.7 One of the most important properties of motor oil in maintaining a lubricating film between moving parts is its viscosity. The viscosity of a liquid can be thought of as its "thickness" or a measure of its resistance to flow. The viscosity must be high enough to maintain a lubricating film, but low enough that the oil can flow around the engine parts under all conditions. The viscosity index is a measure of how much the oil's viscosity changes as temperature changes. A higher viscosity index indicates the viscosity changes less with temperature than a lower viscosity index.
Motor oil must be able to flow adequately at the lowest temperature it is expected to experience in order to minimize metal to metal contact between moving parts upon starting up the engine. The pour point defined first this property of motor oil, as defined by ASTM D97 as "... an index of the lowest temperature of its utility ..." for a given application,8 but the "cold cranking simulator" (CCS, see ASTM D5293-08) and "Mini-Rotary Viscometer" (MRV, see ASTM D3829-02(2007), ASTM D4684-08) are today the properties required in motor oil specs and define the SAE classifications.
Oil is largely composed of hydrocarbons which can burn if ignited. Still another important property of motor oil is its flash point, the lowest temperature at which the oil gives off vapors which can ignite. It is dangerous for the oil in a motor to ignite and burn, so a high flash point is desirable. At a petroleum refinery, fractional distillation separates a motor oil fraction from other crude oil fractions, removing the more volatile components, and therefore increasing the oil's flash point (reducing its tendency to burn).
Another manipulated property of motor oil is its Total base number (TBN), which is a measurement of the reserve alkalinity of an oil, meaning its ability to neutralize acids. The resulting quantity is determined as mg KOH/ (gram of lubricant). Analogously, Total acid number (TAN) is the measure of a lubricant's acidity. Other tests include zinc, phosphorus, or sulfur content, and testing for excessive foaming.
The NOACK volatility (ASTM D-5800) Test determines the physical evaporation loss of lubricants in high temperature service. A maximum of 14% evaporation loss is allowable to meet API SL and ILSAC GF-3 specifications. Some automotive OEM oil specifications require lower than 10%.
Privacy urban bus
City bus can be approved for use by the city after a thorough check its technical condition, it must be not only efficient, but also to meet all the standards required for vehicles to carry passengers on the urban areas. The most important will always be the safety and comfort of passengers, for which you need to take care of before a vehicle is moving, and in the course of passenger transport. Repairing city bus it will be made after finding in it the existence of any defects that might jeopardize the safety of passengers. On the other hand, making such activities as engine oil or brake, may belong to the same driver or service personnel.
Suitable building for garage
Own car repair shop is the biggest dream of many mechanics. But before we start to run their own business, conical is to find a suitable location, and - a building that will provide comfortable working conditions. Ideally, you will find in it both the canal and on the lift. In addition, we find such an object, which will include space for storage of spare parts, and of course the social room. You should also remember the special containers for screws and plates on the wall where suspend wrenches and other tools - this will facilitate the maintenance of order. A good solution is a building next to which there is a place for parking cars repaired.