Automatic Transmission fluid (ATF)

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What is Transmission Fluid?

Transmission fluid is a type of oil used for the hydraulic transmission of forces within a vehicle. Different fluids are used for automatic and manual transmissions, as well as different vehicles makes and countries of origin. It is very specialized and contains a wide variety of additives. These additives serve a number of purposes, such as rust inhibitors, anti-wear additives, surfactantsSurfactants are compounds that lower the surface tension of a liquid. (ref: wikipedia) to clean and protect metallic surfaces and anti-foam agents. All of these additives are added so that the resulting mixture meets the high standards set for automatic transmission fluids. These standards regulate everything from color and flash point  The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. (ref: wikipedia)to wear resistance. Transmission fluid is typically colored red or green in order to distinguish it from other vehicle fluids and oils.

Different Types of Transmission Fluid

There are a number of different variations on transmission fluid. These variations are dependent on whether the vehicle is manual or automatic. The make and model of the vehicle, as well as its age, also determine what transmission fluid is recommended by the manufacturer. In addition, transmission fluids are divided between organic petroleum-based oils and synthetic oils.

Synthetic oils offer better performance all-around than organic oils. They are more resistant to heat and friction. Unsurprisingly this higher performance comes at an increased cost. Organic oils are perfectly serviceable and are often much cheaper.

Originally, only two types of transmission fluids were used. These were Type A and Type F, used by General Motors and Ford vehicles respectively. As time passed, other fluids were developed. Today, these include Dexron VI, Mercon V, Chrysler ATF+5 and a number of other variants that are used in certain specialty vehicles. Import vehicles, such as Hondas, Nissans and Toyotas have their own particular fluids as well.

In addition, many synthetic transmission fluids claim to meet the OEM specifications for many different vehicles. Some are adequate substitutes, while others might not meet the needs of a particular make or model. Caution is necessary when using a generic synthetic transmission fluid.

Synthetic vs. Mineral (Organic) Transmission Fluids

Synthetic vs. Mineral transmission fluids comparison  required a further indepth look. A detailed discussion can be found here.

Why do Different Manufacturers Require Different Transmission Fluids?

Originally, there were only two major transmission fluids. As time went on, transmissions grew in complexity. Meanwhile, different manufacturers started designing different styles of transmission in their vehicles. More manufacturers meant more designs for transmissions, each with their own specific requirements for the additives in their transmission fluids. At the same time, different countries imposed different laws about what can and cannot be in a transmission fluid. The result is that different automakers have different standards for transmission fluids.

Today the largest concern is shift quality. Each automaker requires a specific level of friction in their transmission fluid. Having too high a degree of friction will cause damage to the components of the transmission. Conversely, having too low a degree of friction will make it harder for the gears to engage when shifting occurs. Each automaker knows the precise level required for optimal performance of their vehicles.

Another reason each automaker specifies their own level is to differentiate themselves from other manufacturers. If every transmission required the same transmission fluid, no company could assert dominance over the fluid market. With different companies requiring different fluids, each company is now allowed to create and market their own fluid. This requires the consumer to purchase transmission fluid from their manufacturer, netting the company more profit overall on the life of the vehicle.

Because of the tactics used to ensure that each car needs its own specific transmission fluid, it is important to use that fluid or a compatible one. Each company makes sure that their transmission fluids are compatible with older model vehicles. A General Motors vehicle that requires the use of Dexron III transmission fluid, for example, will be perfectly safe using the updated Dexron VI fluids. In fact, the Dexron VI fluid might involve a slight performance increase, as it is better and more precisely formulated for use in General Motors vehicles.

Some synthetic transmission fluids claim to work with a wide variety of different makes and models of vehicles. While they may certainly work, they might not work at peak efficiency, and so the vehicle may see a hit in gas mileage. Whether this is true or not depends on the fluid and the vehicle model on an individual basis.

The Effects of using Improper Transmission Fluid

Because each manufacturer has different requirements for the transmission fluid they use, using the wrong fluid can have negative consequences. The degree of consequence depends on how far out of specifications the fluid added is compared to the fluid required.

At the bare minimum, using the wrong fluid may have no effect. Some fluids are designed to have specifications exceeding those of most common transmissions. This is especially common for generic synthetic transmission fluids. The transmission will operate fine and the vehicle will not suffer for it.

If the transmission fluid is slightly out of specifications, the vehicle will suffer in minor ways. It might take longer to shift into gear or to change gears while driving. The vehicle might see a decrease in fuel efficiency related to inefficient shifting.

Transmission fluids that are too far out of specifications begin to cause more damage. Too much friction can cause certain components to erode faster than normal, causing excessive wear and tear on the transmission. At best, this will be caught early enough that the damage is minimal. The fluid can be flushed out and the proper fluid added with relative ease. At worst, the damage may remain hidden until something fails in a catastrophic manner, requiring the replacement of the transmission entirely.

Mixing fluids is another issue. Mixing brands can cause issues because the resulting solution does not meet the specifications of either fluid. This can be an issue if a car breaks down and the only nearby source of fluid is a generic fluid not rated for a specific vehicle.

Mixing organic and synthetic fluids also can cause an issue with heat distribution. The largest danger to a transmission is the fluid overheating and burning. If the resulting mixture has a flash point below the temperature of the transmission in operation, the fluid can burn and cause a large amount of damage tot he transmission itself. It is best not to mix fluids and to stick with the manufacturer recommendation.

How frequently to change transmission fluid?

Under Progress; i am developing a comprehensive list by vehicle type. A general rule though is 50,000 Km.

What type of transmission fluid to use with my car?

We are currently testing a new tool which shows the type of transmission fluid to use with your car can be found here:

http://mistertransmissiontoronto.org/my-transmission-fluid-type-finder/