Transmission oils for motor vehicles by ADDINOL
ADDINOL automotive transmission oils offer a reliable solution for almost any application. These include high-load hypoid transmission, synchronised and unsynchronised manual and steering transmission as well as distribution transmission of car, truck, tractor, forestry and construction machines as well as stationary plant.
Transmission oils from ADDINOL can fulfil even the most extreme requirements. They offer effective protection against wear and even ideal friction behaviour for cold starts. In addition, our transmission oils provide optimum viscosity, at both low and high temperatures. For example, our Multi Transmission Fluid 75 W 80 or our transmission oils of the GH series ensure the maximum lifetime for your transmission.
Your benefits at a glance:
- Excellent flow properties
- Optimised friction behaviour
- Suitable for the highest loads at high and low temperatures
- Reliable protection against wear and corrosion for the longest transmission lifetime
- Increased oil changing intervals
- Maximum energy efficiency through safe and reliable lubrication
- Excellent, personal service thanks to our Application Technology
Information about transmission oils
Requirements for transmission oils
The lubrication of a transmission places special demands on the lubricant used. When loaded tooth flanks mesh together, a high pressure acts on the lubricant, which must constantly form a lubricating film in order to avoid direct contact of these friction partners. If the metal surfaces of the tooth flanks meet directly, a friction condition (mixed friction) could occur in which the tooth surfaces may be damaged severely by increased wear. This could result in damage that might lead to the failure of a gearbox. Transmission oils shall prevent this.
The most important requirements for transmission oils are:
- Lubrication of the friction partners
- Compatibility with sealing materials
- Optimised friction behaviour for shifting operations
- Cooling of the transmission by heat transfer to the housing
- Protection against corrosion, wear, deposits and foam
- Optimised viscosity for high temperature and low temperature flowability
- Resistance to ageing due to oxidation and temperature variations
Transmission oils are required in almost all motor vehicles. There are transmission oils for cars, trucks, tractors and motorcycles. In many vehicles, you might find several different types of transmission. Manual transmissions, differentials, or axle drives – each requires special lubricants. In addition, there is the distinction between lubricants for manual transmissions and lubricants for different types of automatic transmissions.
Composition of transmission oils
Like engine oils, transmission oils consist of base oils (mineral or synthetic) and additive combinations tailored to the particular demands in the field. The manufacturing process of a transmission oil is basically the same as that of other automotive oils. In comparison to engine oils, however, the additive content can be significantly higher, since transmission oils in commercial vehicles are intended to be changed at intervals of up to 750,000 km.
The application of EP additives is very important for transmission oils. They prevent scuffing of the metal-to-metal friction partners. Axle drives require a high portion of EP additives, which usually consist of phosphorus and sulphur components. However, sulphur components can cause corrosion and ageing problems, so corrosion inhibitors and antioxidants must be added as compensation. A simple example like this already shows that additives in lubricants have to be matched carefully to each other. This requires experience and tests by the lubricant manufacturer in order to find an optimal interaction of the additives in the oil. However, overdosing due to the addition of additives to finished fluids by end users can quickly reverse the advantages of a specifically tailored transmission oil.
In addition, transmission oils have to resist high and low temperatures, prevent corrosion and remove impurities from the oil circuit.
Important additives in transmission oils are:
- EP additives (Extreme Pressure - to protect against scuffing)
- AW additives (Anti Wear - to protect against wear)
- Friction modifier (not always the lowest, but an optimal friction coefficient is important)
- Defoamer (reduction of foam formation)
- Corrosion inhibitors (reduction of corrosion and neutralisation of acids)
- Viscosity-Index improver (optimisation of viscosity-temperature behaviour)
- Pour Point Depressant (improvement of low temperature behaviour)
- Antioxidants (reduction of oil ageing)
Viscosity of transmission oils
The appropriate viscosity of a transmission oil contributes significantly to maintaining the required lubricating film thickness between the gear components. It is a simplified description of the internal resistance of an oil to flow. For driveline fluids it is classified worldwide into viscosity classes according to the US-American standard SAE J306 (Society of Automotive Engineers). There are viscosity classes from SAE 80 to SAE 250. The classification is based on the kinematic viscosity (measured in mm²/s) at 100°C. The higher the number, the thicker the oil.
Similar to engine oils, there are also viscosity classes for low-temperature applications, marked with the letter "W" from 70W to 85W (capable of flowing at temperatures down to -55°C or -12°C respectively). These "W" or winter classes classify the oils according to their flowability at low temperatures. Classification is based on the temperature at which the dynamic viscosity measured with a Brookfield viscometer does not exceed 150,000 mPa*s. Consequently, the Brookfield value of a SAE 80W automotive transmission oil at -26°C must not exceed 150,000 millipascal seconds.
|SAE class||Max. Brookfield viscosity of 150,000 mPas at temperature in °C||Min. kinematic viscosity at 100°C in mm²/s||Max. kinematic viscosity at 100 °C in mm²/s|
For multigrade oils such as 80W-90, the "80W" describes the low temperature properties, the "90" the thickness of the oil. The limit values of both classes have to be met. Transmission oils with SAE 80W-90 and 85W-90, which are still widespread, are mainly produced from mineral base oils. For thicker oils such as 80W-140 an additional shear-stable viscosity index improver is needed to meet the cold flow requirements down to -26°C. For even lower temperature levels with 75W or 70W at a viscosity level of SAE 90 or higher, the formulation effort will increase rapidly. For this purpose, synthetic base oils according to API group III, IV or V are required to guarantee the flowability of automotive transmission oils even at temperatures of -55°C and below.
The choice of the viscosity depends on the requirements on an optimized lubricating film thickness for the respective transmission application. If the oil is too thick, the gears must work against the viscosity. This results in higher splash losses, which reduce the efficiency, and higher temperatures, which cause the oil to age faster. However, if the viscosity is too low, the lubricating film thickness required to separate the friction partners cannot be achieved. The outcome is a higher risk of damage due to faster wear under mixed friction conditions. Which viscosity is the most suitable for your transmission is specified by the respective vehicle manufacturer. Follow the instructions in your operating manual or rely on the advice of our application technology experts.
Classification of transmission oils according to API
The American Petroleum Institute (API) does not only define international specifications for engine oils. With the classification of automotive transmission oils in six GL classes (Gear Lubricant), the API has specified the most common classification system. It defines the corresponding basic requirements depending on the field of application. Depending on the predominant load regime in the gearbox, a different composition of additives will be required.
The following table provides an overview:
|GL-1 (inactive)||Oils for gearboxes with low contact pressure and low sliding speeds||Oils w/o additives were usually sufficient, antioxidants, corrosion protection additives, defoamers or pour point reducers can be used. Friction modifiers or EP additives are not allowed.|
|GL-2 (inactive)||Oils in worm gears for axles vehicles that are not covered by API GL 1 with regard to load, temperature and sliding speeds.||Oils with wear-reducing additives, but without EP additive requirements|
|GL-3 (inactive)||Oils for manual gearboxes and bevel transmissions in trucks with light to medium speed and load requirements.||Oils with EP additives for higher load carrying capacity than API GL-1 oils, but below requirements for API GL-4|
|GL-4||Oils for bevel transmissions and hypoid gearboxes in axles under light load and speed conditions as well as for selected shift and transaxle gearboxes||Oils with EP additive content above GL-3 level and additional requirements on corrosion protection|
|GL-5||Oils especially for hypoid gears (differential) in axle drives at high speed and/or low speed and high torque conditions||Oils with high content of EP additives and requirements on corrosion protection and ageing stability|
|GL-6 (inactive)||Oils for gearboxes with very large pinion offset (the design has not been accepted - performance tests required for API GL-6 are no longer available)||Oils with very high EP additives beyond the API GL-5 dimension|
|MT-1||Oils for non-synchronized manual transmissions in buses and trucks||Oils with high requirements on thermal stability, sealing compatibility, and higher corrosion and wear protection than oils for API GL‑5|
The API classes GL-1, GL-2, GL-3 and GL-6 were rated "inactive" in 1995. However, transmission oils can still be marketed with these specifications.
It is not recommended to mix transmission oils of different API classes with each other. Manufacturer information should also not be ignored. If your car needs an API GL-5 oil, no GL‑3 or GL-4 oil should be added. GL-3/4 oils with their additives will not keep up with the high loads and cannot prevent accelerated wear. If you otherwise fill a GL-5 oil into a manual gearbox that is designed for GL-3 or GL-4, the usually lower friction will lead to slippage of the synchronizer in the gearbox. In the worst-case scenario, the whole circuit will fail.
OEM performance classes
Classification according to SAE and API is only a simplified basis. The actual performance of transmission oils is determined by meeting additional specifications directly specified by transmission or vehicle manufacturers (OEMs = Original Equipment Manufacturers). OEMs define requirements for specific transmission or vehicle types of a brand. When purchasing transmission oils, therefore, pay attention to the required specifications or approvals. Follow the instructions in your operating manual or rely on the advice of our application technology experts.
Important OEM performance classes of transmission oils are:
- Mercedes-Benz operating regulations
- MAN Werknorm
- ZF TE-ML
- VW standards
- Scania STO
- Volvo STD
For vehicles with automatic transmissions, General Motors and Ford are leading manufacturers. Their systems around the specifications GM DEXRON and FORD MERCON were forerunners and are still adapted by OEMs today. Meanwhile, they have often been replaced by individual specifications from OEMs. Individual performance classes for ATFs are also published by Mercedes-Benz, VW and many Asian manufacturers. The API classes, on the other hand, do not apply to automatic transmission fluids.
Automatic Transmission Fluids - ATFs
In Europe, about 35% of all passenger cars and more than 50% worldwide are equipped with automatic transmissions with an upward trend. Modern automatic transmissions are efficient and sporty - largely independent of the design principle. A distinction is made here between three systems, each of which has its own advantages and disadvantages and puts special demands on the fluids. There are torque converter automatic transmissions (AT - most widely used), dual clutch transmissions (DCT - also common and increasingly popular) and continuously variable transmissions (CVT - small market share, more popular in Asia).
|Automatic step converter|
Different automatic transmission fluids (ATFs) need to be used to optimize the operation of each of the different types of automatic transmissions. ATFs are optimized to meet the requirements of the transmissions, as they take on more versatile tasks than classic gearbox lubricants. ATFs are working media for internal hydraulic circuits (e.g. valve control), ensure the required friction of multi-disk brakes and clutches during shifting operations, protect the individual transmission stages and bearings against wear and corrosion, or serve as pressure transmission medium for torque converters.
The aim of modern automatic transmissions is not only increased comfort of driving, but also improved transmission of power, which in turn results in lower fuel consumption and lower emissions. To fulfil all these tasks, ATFs require an individually composed additive system that differs significantly from oils for axle drives or manual transmissions.
Top up transmission oil
Similar to engine oil, transmission oil can lose volume due to constant load or leakage. If the oil level in the transmission unit drops too low, inadequate lubrication occurs, which promotes wear and corrosion in the transmission unit.
Oil level measurement in a gearbox is not always possible without problems. Manual gearboxes usually do not have an oil dipstick. The oil is filled in by the manufacturer and normally only needs to be changed when repairs to the gearbox become necessary. However, if your gearbox makes noises or is stuck regularly, it is worth having it checked by a workshop. These can be signs of additive degradation. However, it may also indicate a low oil level. In this case, the oil level can be replenished before long-term damage occurs. If necessary, a problem that led to a drop in the oil level can also be solved. If a car loses transmission oil, this may be due to the following causes:
- Defective sealing rings on the clutch side (oil escapes between engine and transmission housing)
- Leakage at the oil drain plug, filler plug or housing seal (oil leaks from the drive or cardan shaft)
Automatic transmissions often have an oil dipstick. Where this can be found is given in the operating manual. If your car is not equipped with an oil dipstick, the level can possibly be checked via an electronic device. We do not recommend manual testing in a sealed gearbox. This is a complicated process that requires good craftsmanship. In this case, have the oil level checked by a workshop, e.g. during the annual inspection.
If you have an oil dipstick for your gearbox, you can read the level as on the engine. Pull out the dipstick, clean it and re-insert it. Afterwards you can recognize the level by the marking. If the oil level in the transmission unit is actually too low, top up the suitable transmission oil in small quantities. Check the oil level again and again until the desired quantity is in the transmission unit. Too much oil should not be filled either, as the oil pressure will then no longer be correct. Draining the transmission oil is also quite complicated.
Change transmission oil
Oil changes may also be necessary for automotive transmissions. Depending on the manufacturer, so-called lifetime fillings are designed for an average service life of the vehicle of around 80,000 to 150,000 km. Certain transmission types require shorter intervals (e.g. 60,000 km for dual clutch transmissions). However, passenger cars often achieve the double or the triple of this mileage. Especially for trucks with change intervals of 150,000 to 750,000 km for transmission oils, several oil changes will be necessary during the lifetime of the vehicle. Even for cars that do not reach such mileages so quickly, it is advisable to change the transmission oil every six to eight years, since base oils and additives can be subject to ageing effects due to regularly changing ambient conditions. The transmission oil may change its viscosity after a long period of use and will then no longer build up the required lubricating film. It no longer dissipates heat sufficiently or can no longer build up required pressures. Thermal stress or condensation can lead to additive degradation, which in turn can cause unpleasant shifting behaviour. Just have the oil level in the transmission checked regularly, especially for older cars. A rough guide value for the change interval of a transmission oil is about 80,000 kilometres. Follow the instructions in your operating manual.
Of course, it is possible to change the transmission oil yourself. However, this is much more expensive than changing the engine oil. The process requires appropriate tools (oil change device and lifting platform), specialist knowledge and craftsmanship. Some gearboxes, for example, have to be removed for a change. We therefore recommend that you have the transmission oil change carried out in a garage. There are two possibilities:
- Drain the transmission oil and fill in the fresh oil. The disadvantage is that waste oil remains in the nested structure of the gearbox and pollutants remain in the gearbox. However, the variant is less complex and less expensive.
- The complete dismantling of the gearbox including the complete removal of the waste oil by flushing. The variant is expensive because it is time-consuming, but much more thorough.
The costs for the complete change of the transmission oil vary depending on the vehicle type. In any case, the process is cheaper than the purchase of a new gearbox if it is damaged by inadequate lubrication.
What happens if transmission oil gets into the engine?
Carelessness may cause transmission oil to be filled accidentally when refilling engine oil. That is not optimal, but also not a reason to panic. As described, transmission oil is similar in composition to engine oil. Due to the different viscosity level and additives, however, it is not recommended to run an engine with transmission oil for a longer period of time. To prevent engine damage or impairment of exhaust after-treatment, a car repair shop should be visited promptly and an oil change carried out. However, if you are forced to drive with the transmission oil in the engine, there will be no imminent danger to the engine. Especially not if the proportion of transmission oil in the engine is only at about 10-20%. Longer distances should be avoided nevertheless.
Dispose of transmission oil
If you carry out a transmission oil change yourself, you will also have to take care of the professional disposal of the waste oil. The same regulations apply to transmission oils as to engine oils. Collect the waste oil in a shatterproof container. Bring it back to the seller free of charge (make sure you keep the receipt for it). The seller is legally obliged to accept the waste oil in the same quantity as sold. Although this regulation also applies to online trading, the customers usually bear the costs of returning the waste oil. Parcel service providers usually classify oil as dangerous goods, which makes shipping cumbersome and expensive. Smaller quantities of waste oil can also be disposed of at the local recycling centres or at some petrol stations. Check with the operator to see if there are any costs. Under no circumstances should you dump the old transmission oil into the household waste or the environment. If oil gets into the groundwater, thousands of litres of clean drinking water will be contaminated. There is a risk of damage to human and animal health. Anyone who is caught disposing of waste oil improperly must also expect high fines. If you have the transmission oil changed by a garage, you will not have to worry about disposing. The garage is responsable to collect the waste oil for professional disposal.