Tech 101: Type A Automatic Transmission Fluid

Choosing a proper automatic transmission fluid may be a complicated process. This is because it is not always clear which oil you should pick for your transmission. Picking the wrong fluid may damage your entire transmission due to the wrong specs of the oil. Therefore, how to choose the right oil is a must-know question in order not to lose your transmission.

When buying transmission oil, you should first identify the type of gearbox equipped in your vehicle. Every gearbox requires a specific oil type with specific viscosity, friction coefficients, and additives. Here, we shall learn more about Type A Automatic Transmission Fluid, have a glimpse of other types, and how choose the proper oil.

Common Purpose of Automatic Transmission Fluid

Just like blood in the human body, oil functions the same in the transmission system. The transmission will never function as expected if it is provided with the wrong oil with different specs. On top of not functioning, the wrong oil can put the whole transmission at risk.

The transmission fluid type chart helps you to know the best choice for your vehicle. Why does every gearbox require a different oil grade? To answer this question, we have to know what is the role of oil in transmission or why we need oil in the transmission?

Transmission oil or (Automatic transmission Fluid) consists of base oil and more than twenty different additives that make it work perfectly. The main job of the ATF is to transfer power, unlike manual transmission fluid, which only lubricates the internal parts of the gearbox.

ATF transmits power produced by the engine to the transmission through the torque converter. It also acts as a surface cooler and cleaner. All the internal parts of the transmission are immersed in oil to cool them down. Besides, the external water cooler is perfect and smooth.

Gear shifting also requires an amount of friction, which is modified by the amount of oil provided between clutch plates. There are numerous types of automatic transmission fluids on the market. Let us discuss them in some detail.

type a transmission fluid
Image Credit:

Type A Transmission Fluid

It was first introduced for general motors car brands in the mid-50s. It was used for all automatic transmissions. Type A Transmission Fluid is the semi-automatic and ‘hydra Matic.’ All brands under the property of general motors such as Oldsmobile, Cadillac, Buick, Chevrolet, Pontiac, GMC, Ford, Mercury, Lincoln, Chrysler, Dodge, Desoto, Packard, and Studebaker used GM Type “A” transmission fluids from 1949–to 1958.

This was until general motors released a new product to replace type A. It was known as Type “A” suffix “A” fluid. This new fluid can stand higher temperatures caused by newly invented torque converters. Type A transmission fluid was a type F transmission fluid equivalent, which was used by ford motors and Toyota. This fluid was less smooth than type A. It was used until the mid-60 until it was replaced with Dexron, Mercon.

Dexron family

Dexron (B) is the first generation of automatic transmission fluids. They were produced after Type A transmission fluid in the mid-60s. When you compare type A transmission fluid vs. Dexron, we will find that Dexron (B) was composed of a more stable, less reactive, and hydrotreated base oil.

It is, therefore, more resistive to heat and anti-oxidation. It was first used by GM dye red as an aid in fluid leakage detection. This fluid is compatible with all Type “A” Suffix “A” and the Type “A” fluids produced by GM and equipped in GM vehicles.

 Dexron II

Dexron II was the successor of the Dexron (B). It was developed by GM in the 70s for better viscosity control and additional oxidation inhibitors. It was also the first GM transmission fluid for electronic transmissions.

Dexron III

Dexron III was used as a torque converter to replace Dexron 2. This generation was considered the most successful. It had improved oxidation and corrosion control. Before the year, 2000, 80 percent of transmission fluid was covered by general motors Dexron 3.


The success of the Dexron continued until 2006, when they introduced Dexron-VI to be used in 6-speed rear-wheel-drive transmissions. Dexron-VI replaced the older types of Dexron II and III, Dexron-VI. It is a low viscosity fully synthetic transmission fluid, and the series continues till today.

Mercon family

It was started by Mercon-type CJ. It was originally developed for ford c-6 transmissions. It was developed to compete with GM Dexron 2, which had the same specs.

Mercon V
Mercon V

 Mercon type H

It was initially made to comply with ford a spec, which differs from general motors, Dexron, and ford type f transmission fluids.

 Mercon V

It was introduced in 1997 to serve the new models which require a low viscosity fluid. This fluid gave a good spread in low time to lubricate the internal parts faster.

 Mercon SP

Mercon SP enhanced friction, which is considered a modified Mercon V model. At that time, every car manufacturer released its specs and additive to the transmission fluid. New types came out, such as HP/J-Matic, which is used by Nissan transmission. It is also used in Infiniti and Subaru.

There is also LT7114l, a special formulation for BMW, Diamond SP-II & SP-Ill for Mitsubishi, Hyundai, Kia, T, T-III, T-IV for Toyota, Lexus, and scion, and ZL ATF for Honda except for CVT models.

All the above types of automatic transmission fluids are used for cars equipped with conventional automatic 4/6 speed transmission. There are other types of transmissions, such as Dual Clutch and CVT transmissions, which require a specific type of oil and special grades of automatic transmission fluids.

Examples for these special grades include full Synthetic CVT Transmission Fluid – SynGard CVT ATF. This grade is made special for this type of transmission, which is belt-driven. The transmissions are very sensitive to the oil grade. Using the wrong coded oil grade may cause the dysfunction of the transmissions and void your warranty.

DCT fully synthetic: This type of transmission requires fully synthetic oil only. It must have additives that increase the temperature coefficient. This is because the transmission may fail when exposed to high temperatures. Therefore this transmission should remain as cold as possible.

How to Check and Add Transmission Fluid, YouTube Video

Final Words

We have got to know the type A automatic transmission fluid, how it started, and evolutionary change in the field of automatic transmission fluids. Transmission fluids have a big effect on every car. It is something that every car owner should pay attention to. One should also pay attention to the type of fluid that should be used in the car. If you are not sure, check the transmission fluid compatibility chart. The chart will give you the information you need about the grade you should use in your car as certified by the car manufacturer. This will help you not to void the warranty of the transmission, which will cost you a fortune if it fails.

Learn more:

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

Recent Posts