Engine Lubrication

Engine Lubrication

The engine lubrication system is to distribute oil to the moving parts to reduce friction between surfaces. Lubrication plays a key role in the life expectancy of an automotive engine . If the lubricating system fail, an engine would succumb to overheating and seizing very quickly. An oil pump is located on the bottom of the engine. The oil is pulled through a strainer, by the oil pump, removing larger contaminants from the mass of the fluid. The oil then forced through an oil filter under pressure to the main bearings and the oil pressure gauge. It is important to note that not all filters perform the same. A filter’s ability to remove particles is dependent upon many factors, including the media material (pore size, surface area and depth of filter), the differential pressure across the media, and the flow rate across the media. From the main bearings, the oil passes into drilled passages in the crankshaft and the big-end bearings of the connecting rod. The oil fling dispersed by the rotating crankshaft lubricates the cylinder walls and piston-pin bearings. The excess oil is scraped off by the scraper rings on the piston. The engine oil also lubricates camshaft bearings and the timing chain or gears on the camshaft drive. The excess oil in the system then drains back to the sump.

ENGINE OIL- Motor oil, Engine oil, or engine lubricant is any of various substances comprising base oils enhanced with various additives, particularly antiwear additive in addition to detergents, dispersants and, for multi-grade oils, viscosity index improvers. Motor oil is used for lubrication of internal combustion engines. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge (one of the functions of dispersants and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves sealing of piston rings, and cools the engine by carrying heat away from moving parts. Most motor oils are made from a heavier, thicker petroleum hydrocarbon base stock derived from crude oil, with additives to improve certain properties

The Society of Automotive Engineers (SAE) has established a numerical code system for grading motor oils according to their viscosity characteristics. The original viscosity grades were all mono-grades, e.g. a typical engine oil was a SAE 30. This is because as all oils thin when heated, so to get the right film thickness at operating temperatures oil manufacturers needed to start with a thick oil. This meant that in cold weather it would be difficult to start the engine as the oil was too thick to crank. However, oil additive technology was introduced that allowed oils to thin more slowly (i.e. to retain a higher viscosity index); this allowed selection of a thinner oil to start with, e.g. "SAE 15W-30", a product that acts like an SAE 15 at cold temperatures (15W for winter) and like an SAE 30 at 100 °C (212 °F).

Therefore, there is one set which measures cold temperature performance (0W, 5W, 10W, 15W and 20W). The second set of measurements is for high temperature performance (8, 12, 16, 20, 30, 40, 50). The document SAE J300 defines the viscometrics related to these grades.


A single-grade engine oil, as defined by SAE J300, cannot use a polymer viscosity index improver (VII, also viscosity modifier, VM) additive. SAE J300 has established eleven viscosity grades, of which six are considered Winter-grades and given a W designation.


The temperature range the oil is exposed to in most vehicles can be wide, ranging from cold temperatures in the winter before the vehicle is started up to hot operating temperatures when the vehicle is fully warmed up in hot summer weather.


Energy is transmitted from a power source to a terminal point through Gears that change speeds, direction and torque. Automobile Transmission is generally of two types, namely manual transmission and automatic transmission. In manual transmission system, driver drives the vehicle with the help of a hand-operated gearshift and a foot operated clutch. Where as automatic transmission, automatically changes the gears with regard to speed of the vehicle. The primary components of automatic transmission include planetary gear sets, hydraulic system, seals and gaskets, torque converter, governor, modulator and computer. Lubricant provides two primary benefits: to lubricate the teeth and to remove heat generated from the gear operation. If the correct lubricant is selected for use in a gear system it will provide slip-free power transmission at high mechanical efficiency, with good reliability, low maintenance, and long life.

GEAR OIL-Gear oil is a lubricant made specifically for transmissions, transfer cases, and differentials in automobile, trucks, and other machinery. It is of a high viscosity and usually contains organosulfur compounds. Some modern automatic transaxles (integrated transmission and differential) do not use a heavy oil at all but lubricate with the lower viscosity hydraulic fluid, which is available at pressure within the automatic transmission. Gear oils account for about 20% of the lubricant market.[1]

American Petroleum Institute (API) established a performance grading system for gear oils (mostly automotive gear oils). According to the system gear oils are designated by the letters GL (Gear Lubricant) followed by a number 1,2,3,4 or 5:

  • GL-1-GL-1 gear oil has rust and oxidation protection effect but it does not contain extra pressure (EP) additives. the oil is used in low load applications only.
  • GL-2-GL-2 gear oil contain more additives than GL-1, but without EP effect. It is used in medium loaded worm gears.
  • GL-3-GL-3 gear oil possesses light EP effect. It is used in non-hypoid gears.
  • GL-4-GL-4 gear oil possesses moderate EP effect. It is most widely used oil.
  • GL-5-GL-5 gear oil possesses high EP effect. It is used in hypoid and other highly loaded gears.


As per ASTM D 288(American Society for Testing and Materials) lubricating grease can be defined as: "A solid to semi fluid product of dispersion of a thickening agent in liquid lubricant. Other ingredients imparting special properties may be included" . Greases are typically applied in areas where a continuous supply of oil cannot be retained, such as open bearings or gears. There are numerous applications for grease, most are for lubricating bearings of various types. There are two main categories of bearing i.e., plain or anti friction. Gear greases consist of rosin oil, condensed with lime and stirred with mineral oil, with some percentage of water. Special-purpose greases contain glycerol and sorbitan esters. They are used, for example, in low-temperature conditions. Some greases are labeled "EP", which indicates "extreme pressure". Under high pressure or shock loading, normal grease can be compressed to the extent that the greased parts come into physical contact, causing friction and wear.