Oil Analysis
Flash Point
ASTM D 92
Flash Point is referred to the minimum temperature of a petroleum product or other combustible fluid at which vapour is produced at a rate sufficient to yield a combustible mixture. Specifically, it is the lowest sample temperature at which the air vapour mixture will “flash” in the presence of a small flame.
Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively non-volatile or non-flammable material. For example, an abnormally low flash point on a test specimen of engine oil can indicate gasoline contamination
The flash point can be used to determine the transportation and storage temperature requirements for lubricants.
Color (Lubricant)
ASTM D 1500
The shade and intensity showed when lubricating oil is viewed under specific conditions.
The test is used for manufacturing control purpose and is important since the colour is readily observed by the costumer. The colour of lubricating oil is not always a reliable guide to product quality and should not be used indiscriminately by the costumer in writing specifications for purchase. Where the colour range of grade is known, a variation outside the established range indicates possible contamination with another product.
Sulphated Ash
ASTM D 874
Sulphated ash is defined as the residue remaining after a sample has been carbonized (i.e. combusted), and the residue subsequently treated with sulphuric acid and heated to constant weight.
This test method covers the determination of the sulphated ash from unused lubricating oils containing additives and from additive concentrates used in compounding. These additives usually contain one or more of the following metals: barium, calcium, magnesium, zinc, potassium, sodium, and tin. The elements sulfur, phosphorus, and chlorine can also be present in combined form.
Pour Point
ASTM D 97
For countries that possess cold weather climates, the performance of lubricants in lower temperatures is of great importance. The pour point of a lubricant is defined as the lowest temperature at which movement of the test specimen is observed under the prescribed conditions of the test. . A reduction in the pour point can be achieved through the use of so-called pour point enhancers to “winterize” the fuel.
The pour point of a lubricant is the lowest temperature at which the lubricant will pour or flow when it is chilled without disturbance under specified conditions.
Kinematic Viscosity
ASTM D 445
Measurement of a fluid resistance to flow under gravity at a specific temperature (usually at 40oC and 100 oC).
Viscosity Index
ASTM D 2270
A measure of a fluid’s change of viscosity with temperature is called Viscosity Index (VI). The higher the viscosity index the smaller the change in viscosity with temperature.
Higher the viscosity index indicates the smaller change in viscosity with increase temperature of lubricating oil.
Specific Gravity
ASTM D 129
Specific gravity is the ratio of weight of a given volume of a substance to the weight of an equal volume of water at stated temperature.
Accurate determination of the density, relative density (specific gravity), or API gravity of petroleum and its products is necessary for the conversion of measured volumes to volumes or masses It is used to measure the volume of fluid.
Total Base Number
ASTM D 2896
The amount of per chloric acid expressed in term as equivalent weight of milligram of KOH required to titrate the basic constituents present in 1 gram of sample is the Total Base Number.
Total base number (TBN) is a measure of a reserve alkalinity of a lubricant.
The test is relevant to internal combustion engines due to the acidic by products of combustion generated when gasoline and diesel fuel are burned. These by products, including SOx, NOx, and others enter the crankcase via blow-by gases getting past the piston rings.
In addition to acids entering the engine crankcase from blow by, acids are normally generated in other areas of the engine due to heat, oxidation, and other chemical processes.
In an effort to counter the corrosive effect of acids on engine parts, constituents are added to the oil (oil additives) that have basic properties. As bases, they act to neutralize the acids in the engine. The additive commonly used is calcium sulfonate. Others, however, including magnesium sulfonate, phenates, and salicylates are also used. In addition to contributing to the TBN of a lubricant, these additives are multifunctional in that they are also highly valued as dispersant additives.
In an effort to strike a balance, the total base number of new oil is typically in the range of 7 to 10 for gas engines and 10 to 14 for diesel engines. When the TBN in used oil drops below 3, it typically indicates the need for an oil change.