When choosing an oil, an experienced motorist always takes into account its most important characteristic - viscosity. This parameter is directly related to the performance of an automobile engine; its resource, throttle response, the possibility of easy start-up in winter.
If we speak in an understandable, not "scientific" language, then the viscosity of automobile engine oil is its ability to lubricate the surfaces of rubbing engine parts, provided that fluidity is maintained. At first glance, the definition is simple, but it is the viscosity of the oil that most of all depends on the temperature, directly affecting the operation of the mechanisms that need lubrication.
Features of the work of car oils
The main task of any automobile oil, incl. and motor, the formation of an oil film between the moving parts of the engine, which should not allow dry friction. Also, engine oil contributes to minimal friction, provided the cylinder chambers are tight. The real oil temperature is constantly changing and can reach 140-150 ° C; the readings that the driver sees on the dashboard tell him only about the operating temperature of the coolant. The latter really has stability and on average (on a warm engine) is about + 90 ° C.
It is quite difficult to create a substance that would lubricate engine parts equally well over a wide temperature range; therefore, manufacturers take into account many parameters when developing brands of oils. Most of them are displayed on the label in the form of an alphanumeric code that characterizes the operational characteristics of the car oil.
Engine oil coding
The viscosity grading of engine oils was developed by the Association of American Automotive Engineers (or SAE) and is now accepted in most countries around the world. The purpose of the classification is to define the operating temperature range at which the engine will feel "comfortable".
For decoding, you can take the marking on any car oil label; for example SAE 10W-40. The abbreviation of the Association of Automotive Engineers is followed by the number 10, which defines the viscosity of an oil at specific temperatures. If we subtract the number “forty” from “ten”, we get “minus thirty”. This means that this temperature provides the ability of the oil pump to pump the lubricant without allowing dry friction. If we subtract 35 from the first digit in the designation, then we get the number minus 25, which will denote the minimum ability of the starter to turn the engine crankshaft.
The second number in the designation (in this case 40) indicates high-temperature viscosity. The larger it is, the higher the viscosity at high temperatures (i.e., increased loads) will be. It is best to ask the manufacturer directly for the optimum viscosity value for a particular vehicle.
