Why So Many Automatic Transmission Fluids?

Many people regularly ask me why there are so many different automatic transmission fluids recommended by the various vehicle manufacturers.

Let me begin by stating ” There is no such thing as a universal ATF and you cannot up-treat an ATF, by adding aftermarket additives.” An article supporting this was published in the Lubes ‘n Greases magazine in June 2015 already.

According to my Castrol handbook from 1991, 30 years ago, there were six automatic transmission fluids available, namely: GM Type A Suffix A; Dexron; Dexron II; Dexron IIE; Ford M2C 33 (Ford Type F) and Mercon fluid. This excluded the two commercial Leyland and Allison transmission fluids shown on the same page. Nowadays, we have many more. Companies like Ravenol (Ravensberger Schmierstoffvertrieb GmbH) have over 40 different OEM-recommended and approved automatic transmission fluids (ATF’s).

Using the OEM-approved lubricants is in the best interests of owners and their vehicles. This is because vehicle manufacturers often have vastly different specifications for the range of transmissions they manufacture or supply in their vehicles, and one is often not suitable for another. An example is that early BMW automatic transmissions used only hydraulic control with no electronic intervention. Subsequent refinements, such as Electro-Hydraulic (EH) transmissions, introduced a new acronym: EGS (Elektronisch Getriebe Steurung) − electronic transmission control. These modern automatic transmissions are now able to achieve better fuel economy, reduced engine emissions, greater shift-system reliability, improved shift feel, improved shift speed and improved vehicle handling, but only when the correctly specified automatic transmission fluid is used.

OEMs like BMW provide their customers with automatic-transmission options such as ZF and GM’s Hydra-Matic, which require very specific fluids.

OEM specifications often denote a minimum acceptable performance level, to which are often added particular OEM requirements or tighter tolerances on a general ATF specification.

Extensive testing therefore helps OEMs maintain an active list of approved lubricants. An example of such a reference to specification and approved fluid, may be seen in all BMW manuals where the specified automatic transmission fluid is always accompanied by the following text:

“The automatic transmission provides pressure regulated hydraulic fluid which is filtered for all of the transmission’s functional requirements. All BMW automatic transmissions are designed to operate with specific fluids. Use of non-approved oil will cause malfunctions and irreparable transmission damage which is not covered by BMW warranty.” (Please pay careful attention to the word “will” in that last sentence).

Some mechanics will put an incorrectly specified universal ATF in an automatic transmission – and because it works they believe this is acceptable. This is despite not knowing the long-term effects of using the incorrect fluid, while presuming to know better than the OEM who has spent millions of dollars (or deutschmark, or yen, or rand) in scientific testing of every component of the transmission, over the full expected lifetime of the transmission.

ZF (ZF Friedrichshafen) transmissions are fitted to many vehicles, including Land Rover, VW, Jaguar, Ford, Audi and BMW. The ZF website states the following:

“In modern transmissions, the oil is a ‘constructional component’ that needs to match the different transmission functions and materials as perfectly as possible. ZF transmission oils are especially developed for the individual transmissions and adapted to their specific requirements.”

At Ravenol, we have 45 automatic transmission fluids, which means that BMW are not alone in this requirement of only accepting the use of specific approved fluids in their transmissions. An example of this ever changing requirement is the attached Toyota technical bulletin TC003–99 and Toyota technical bulletin TC006-03 which are both dated 1999/2003. Proof that these requirements have been in place with Toyota for quite some time. As may be seen by Toyota technical bulletin TC003–99, a clear instruction is offered that with the exception of mixing ATF Type T with Type T–IV fluids, different types of fluids must not be mixed. If fluids within the OEM range cannot be mixed, then how can any oil company sanction a multipurpose / universal ATF? In Toyota technical bulletin TC006-03, Toyota states that the new automatic transmission fluid (ATF) “WS” has been introduced on 2004 – 2005 model year 4Runner, Land Cruiser and Prius vehicles. Once again, Toyota warn that ATF “WS” is NOT compatible with any other type of transmission fluid. I have many customers that have learnt this lesson the hard way. Look at the attachment – ATF co-efficient of friction and you will see that Ford specifications like M2C -33G have exactly the opposite frictional curve to Dexron fluids. These are examples of how most OEM’s consider only their own automatic transmission fluids to be suitable for their automatic transmissions. As most oil companies do not provide these types of automatic transmission fluids and the only option that remains, is then to purchase these specialised automatic transmission fluids from the dealer/agent/OEM. Fortunately, Ravenol provides an alternative to these “OEM only fluids” that conforms to the OEM requirements, listing the appropriate OEM part numbers and approvals.

OEMs are demanding longer drain intervals and fill- for-life capability for passenger cars. Automatic transmissions are changing in design from 5 to 6 and 7 speed and now even 9 speed capability, improving drivability and performance. To improve fuel economy, transmission components are lighter, viscosities are lower, despite increased engine horsepower. And now new fuel-efficient transmissions exhibit higher torque and higher operating temperatures. All these factors are stressing the automatic transmission fluid severely. Problems such as transmission shudder, poor shift feel and accelerated wear are becoming more common as drain intervals are increased. Automatic transmission fluids must provide fill-for-life capability, improved fuel economy, anti-shudder, friction durability, shear stability, low-temperature fluidity and improved oxidation stability.

Many lubricant marketers make blanket claims about the suitability of their products for universal use in the consumer marketplace; however, the lubricants marketed by all oil companies cannot be seen as equivalent and compatible. There is no such thing as a universal automatic transmission fluid (ATF), and an ATF cannot be up-treated by the addition of aftermarket additives. The importance of these variations in OEM requirements and specifications is often underestimated or ignored by workshops until a problem arises; and only then do they become concerned about the critical importance of selecting the correct lubricant – almost always at the expense of the vehicle owner.

The above means that vehicle owners should take care when it comes to choosing a workshop to service their vehicle, and pay more attention to the lubricant-quality and brand offered by them. The same amount of care should be exercised by DIY enthusiasts, as advice from spares shops on lubricants is mostly extremely poor, and, in many cases, completely non-existent.

That is it! In a nutshell…..short of coming on a one day Oil Wise seminar on automatic transmission fluids, past and present.

If you want to know which is the correct ATF for your vehicle, please visit our Oil Finder.