API GL-1: In spiral-bevel and worm gear axles and some straight transmission running under intermediate service conditions
API GL-2: In worm gear axles where API GL-1 is not adequate
API GL-3: In straight transmission and spiral bevel gear axles running under intermediate service conditions
API GL-4: In hypoid gears running under heavy service conditions without shock loading
API GL-5: In hypoid gears running under very heavy service conditions with shock loading
API GL-6: In the gears exposed to high pressure, running under heavy service conditions

The classification is made with a figure following a letter (like A3). ACEA standard is divided into two categories. The first category explains the engine in which the oil can be used:
For gasoline engines A,
For diesel automobile engines B,
For lorry engines C,

Meanwhile, the subsequent number identifies the performance level of oil:
For fuel economy 1,
For general purpose (average level) 2,
For high performance 3.

For example, A3 defines high performance oil for gasoline engines, A1 defines the oil for economy purposes for gasoline engines.

The classification is made with two letters. The first letter indicates engines among gasoline (S) or diesel (C) for which the oil is suitable, and the second letter indicates performance value of the oil in the same group. Performance classification is made between A-J for gasoline engines while A is the lowest, and between C-F for diesel engines in both groups. In gasoline engines: (min. performance) SA..SB..SC..SD..SE..SF..SG..SH..SJ (max. performance) In diesel engines: (min. performance) CA..CB..CC..CD..CE..CF (max. performance)

SAE classification classifies the oil according to viscosity at low and high temperatures different from others, therefore it can be said to be somewhat more detailed. The degree in SAE classification is composed of two figures separated by the letter of W. W means winter and indicates the viscosity of oil at low temperature. For example, 15W in 15W-40. At the same time, this is the base viscosity of the oil, i.e. its intrinsic viscosity prior to the addition of polymer. This shows us how fluent the oil will be at low temperatures and how easy the engine will run because the smaller the figure is the finer the oil becomes. The second figure gives the high heat viscosity of the oil. Such as in the 15W-40. As the number increases, so the oil becomes more viscosity, namely thick when it is hot.

The classification of automotive oils has been done by various organizations and the initials of these organizations have been placed in front of the numbers of tests applied to these oils. These classes identify the performance of the oil.

These abbreviations with explanations are as follows:

SAE: American Automotive Engineers Union
API: American Petroleum Institute
ILSAC: International Lubricant Standards and Approval Committee
ACEA: European Automobile Manufacturers’ Association
MIL: USA Army Lubricant Specifications
JASO: Japan Automobile Standards Organization.

Synthetic oils are the oils produced by chemists as a result of various chemical processes in laboratories.

They’re the oils obtained after distilling the petroleum in refineries.

The substances used to separate two solid objects in general and to provide easy movement by minimizing the friction power, are called lubricant or oil.

It is obtained by mixing various additives into base oils with different viscosity in order to provide physical and chemical properties expected from the product.