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Lubricating oil viscosity.

The viscosity indicates the degree of fluidity of oil, measured at a predetermined temperature. It is also referred to as the thickness of oil.

Short outflow time is low viscosity.

Long outflow time is high viscosity.

SAE.

Motor oil viscosity is determined by the SAE classification system and is expressed as an SAE number. The SAE number does not indicate a sharply defined viscosity, but represents a viscosity range. SAE stands for Society of Automotive Engineers, an association of automotive technicians mainly from America, which aims to standardize the viscosity value of oils. An SAE number has the same meaning all over the world.

SAE number.

The lower the SAE number, the thinner the oil. The higher the SAE number, the thicker the oil. So an SAE-20 motor oil is thinner and has a lower viscosity than an SAE-40 motor oil which is thicker and has a higher viscosity. The viscosity of each oil is highly dependent on the temperature. As the temperature rises, the oil becomes thinner. When it cools, the oil thickens again. The warmer the oil, the lower the viscosity. The colder the oil gets, the higher the viscosity. Any warm oil is thin, but not the same and any cold oil is thick, but not the same.

SAE classification classifies the lubricating oil by viscosity and not by quality.

The classification is based on recording viscosity at 100 degrees Celsius. Oil types that have only been measured at 100 degrees Celsius are indicated by a single number. The letters SAE stand before the number. This includes summer grade oils in the series SAE-20, 30, 40 and 50.

For the thinner winter oils, the viscosity limits have been set at different temperatures from -5 degrees Celsius to 35 degrees Celsius, but also at high temperatures of 100 degrees Celsius, while the pumpability of oil is measured at certain low temperatures. These oil types are indicated by a number followed by a W for winter. This group of winter oils includes: SAE 0W, 5W, 10W, 15W, 20W and 25W.

The SAE code 0W specifies the viscosity of the oil for extremely cold areas. The 25W degree, on the other hand, for areas with very mild winters.

Mono- and multigrade oils.

We distinguish:

* Mono or single grade oils

* Multi-grade oils

* Mono-grade oils

The mono or single grade oils are only suitable for use in winter or only in summer. These oils only cover one viscosity range.

Multi-grade Oils.

Multi-grade oils are summer and winter oils and thus can be used all year round. They are indicated by two SAE numbers. These oils have a low viscosity at low temperatures and a high viscosity at high temperatures.

An example of a multi-grade oil is a SAE 10W40 oil. The first number 10 determines the minimum fluidity (viscosity) at a certain low temperature, at which those values apply. The W after the number indicates that this oil has also been tested at low temperatures and can therefore be used as a winter oil. The last number determines the minimum and maximum viscosity at 100 degrees Celsius of the oil. An SAE 10W40 oil has a viscosity of a 10W oil at cold start and a viscosity at the operating temperature of the engine that is equal to an SAE 40 oil at that temperature.

Viscosity determination.

The viscosity at 100 degrees Celsius is measured with a capillary viscometer. Here, a metered amount of oil flows through a narrow, high-precision glass tube (capillary) where the outflow time is measured. The viscosity obtained in this way is called kinematic viscosity and is expressed in mm 2 / S. This SEA method measures the viscosity of the oil returning from the cylinder head to the engine crankcase.

The European car manufacturers decided in 1985 to also come up with their own regulations (CCMC) in which the oil is tested at 150 ° C and examined for sensitivity to temporary and permanent loss of viscosity. The CCMC determines the viscosity of the oil that is located between the connecting rod bearing and crankshaft journal, cam and ram, piston and cylinder wall. The CCMC viscosity measurement takes place under high temperature and high shear. The abbreviation of this test method is HTHS (HIGH Temperature High Shear).

The viscosity at low temperatures is measured with a dynamic viscometer (CCS = Cold Cranking Simulator = simulation of the cold start) and is expressed in mPa.s. We call the viscosity obtained in this way dynamic viscosity.

The pumpability of the oil at certain low temperatures is measured using a Mini Rotary Viscometer (ASTM D 3829)

The viscosity is clearly visible in the test with balls of equal mass that are simultaneously placed in the tubes with different oil types, the dimensions in which they fall down depends on the thickness of the oil.

Viscosity index.

The viscosity index abbreviated V.I. is expressed in a ratio that indicates the relationship between the fluidity and the temperature of the oil. The higher the V.I. the less influence the temperature has on the viscosity (fluidity) of the oil.

Oil with a low V.I. is thick at low temperature and thin at high temperature. Oil with a high V.I. is less thick at low temperature and less thin at high temperature.

 Multi-grade and synthetic oils have a V.I. between 140 and 190. The V.I. coding number is a quality indication.

Improved dope.

By a V.I. By developing enhancing dope and adding it to mineral base oils, we have succeeded in making multi-grade oils that are less temperature sensitive. The V.I. improving dope only takes effect when the temperature rises and tries, as it were, to keep the oil molecules together. When cold, this dope is inoperative and the oil retains its normal thickness. A thin base oil is used for the production of multi-grade oils. Substances are added to this oil that consist of polymers (very long molecules). These spaghetti-like strands roll up when the oil is cold and stretch (expand) into a kind of braid when the oil is warm. This provides a firm, tough and stable oil film on all moving parts of an engine.

Lubricating oil will always lubricate, as long as it is not diluted by fuel in case of incomplete combustion.
5% diesel oil in it gives a viscosity reduction of 50% (learned at school).
Lubricating oil becomes acidic as a result of moisture and oxygen influences.
Acidification produces low corrosion.