Frequently asked questions / Transmission oils
What is transmission oil?
Transmission oil is a mixture of base oil and additives with very good anti-wear and anti-scoring properties and good stability to thermal oxidation.
What are the functions performed by transmission oil?
The key function of transmission oil is to lubricate hypoid gears in manual and automatic transmissions for cars and trucks.
What are the main types of transmission oil according to its application?
There are two main types:
- Oils for manual transmissions and differential gears. They are also called MTF (Manual Transmission Fluid);
- Oils for automatic transmissions, the so-called ATF (Automatic Transmission Fluid).
What are the main additives used in a transmission oil?
- Anti-wear, anti-scoring and EP (Extreme Pressure) additives. These are substances which prevent the metal surfaces of moving parts from coming into direct contact, and reduce friction.
- Pour point depressant additives lower the freezing temperature and improve the viscosity properties of oils at low temperatures (flow behaviour);
- Corrosion and oxidation prevention additives improve the resistance to oxidation. A well known fact is that the resulting products of oxidation cause corrosion in metals;
What colour are transmission oils for automatic transmissions?
All oils for automatic transmissions are available in a colour different from that of the oils for manual transmissions. Most frequently they are red.
How are MTF oils classified?
The performance parameters of transmission oils are subject to the API classification. Their viscosity properties are defined by SAE J 306.
What are the API operating classifications for MTF oils?
These oils are classified by using GL (Gear Lubricant) ratings. They are subdivided in six performance classes, from GL-1 to GL-6 respectively, of these only 2 are currently in effect.
- GL-1, GL-2, GL-3 and GL-6 – NOW OBSOLETE.
- GL-4 – CURRENT RATING. It is used to indicate the performance characteristics for gears in manual transmissions that operate at extremely high sliding speeds, in particular helical/spiral bevel gears and hypoid gears operating under moderate conditions in cars, and other, automotive equipment with high speed / low torque and low speed / high torque motors;
- GL-5 – CURRENT RATING. Denotes the type of performance characteristics for gears, particularly hypoid, in passenger cars and other vehicle types operating at high speed/shock load, high speed/high torque and low speed high torque. It is designed for heavy duty gearboxes and is used with anti-wear and anti-score EP additives;
- MT-1 – CURRENT RATING. Used for oils designed for heavy-duty manual transmissions that require good thermal stability, resistance to high cyclic temperatures and a better compatibility with copper alloys compared to other API categories. It is typically used for unsynchronized manual transmissions in heavy goods vehicles and buses.
What does the SAE J 306 viscosity classification represent?
The SAE J 306 viscosity classification divides transmission oils into classes according to their kinematic viscosity. The classes are differentiated for hot weather applications, cold weather applications, or for a year-round use - multigrade oils.
How are ATF oils classified?
For ATF products there are no viscosity or operational classifications implemented. Their characteristics and applications are derived from the automatic transmission manufacturers (OEM) specifications.
Which are the most widespread OEM specifications for ATF oils?
Most widely used and largely popular in practice are General Motors (DEXRON) and Ford Motor Company (MERCON) specifications. Apart from them, other manufacturers of automatic transmissions have also introduced their own specifications for ATF oils.
General Motors – DEXRON
TASA – 1957 - DEXRON II E – 1991 - DEXRON III H – 2003
DEXRON II D – 1981 - DEXRON III G – 1997 - DEXRON VI - 2005
Fluids meeting Dexron II (types D, E) specifications can be replaced with higher-class Dexron III fluids. The opposite is UNDESIRABLE!!!
FORD MOTOR COMPANY – MERCON
- ESW M2C 33F/G (G Oil) – 1967
- ESP M2C 138-CJ (CJ Oil) – 1975
- ESP M2C 166 H (H Oil) – 1981
- MERCON WSP M2C 185 A – 1987
- MERCON V – 1996
- MERCON SP – 2005
- MERCON LV (Low viscosity) - 2008
Oils meeting Ford M2C33 -F and -G (G oil) specifications should not be mixed with oils complying with any of the other Ford specifications.
Other ОЕМ specifications:
Chrysler Mopar ATF +4
MAN type 339.X
VW part No.
ZF TE-ML XXZ