Shelf Life and Storage Rules for Transmission Fluid

As a rule, many car owners assume that various technical liquids and lubricants, including transmission fluid, do not have an expiration date , i.e. they can be stored as long as necessary before intended use. But it is a mistaken belief, because the shelf time of transmission fluids is limited by manufacturers. In this article, we will consider this issue in more detail.

How long you can store transmission fluid

Transmission fluids are used to lubricate a wide range of transmission components. The main function of transmission fluids is to create a strong lubricating film around transmission parts. These fluids include a large number of additives, which have properties necessary for efficient operation of the transmission. As for automatic transmissions and CVTs, it is necessary to use a special transmission fluid (ATF) which is responsible for a number of tasks (transferring of torque in the torque converter and being used as an operation fluid in the valve body).

Learn why transmission fluid is crucial for your transmission

As time passes, the transmission fluid filled inside the transmission case becomes contaminated and loses its properties: the fluid ceases to protect the gearbox at high and low temperatures and oxidizing processes take place (“old” fluid cannot resist corrosion efficiently). Thus, it is necessary to change transmission oil regularly. But what about transmission fluid which is put on the shelf and is not used? In this case non-professionals may think that the shelf life for this product is not limited, since the fluid is not exposed to hostile environments, but it’s not that simple.

Useful video on how to interpret date codes on fluid packages

All manufacturers of lubricants for car components usually indicate date of manufacture and expiring date on the container/package for a reason! Commonly, the shelf life of transmission fluids does not exceed more than 5 years from the date of manufacture. However, this period is specified for tightly closed and sealed (and stored under recommended conditions) products.

Fluid manufacturers say that their products can be stored at temperatures between +10 and +25 ºC. Higher temperatures can lead to premature oxidizing processes. Temperatures below recommended limit may cause fallouts of precipitation and appearance of deposits. In case, when the container with transmission fluid is opened, the storage room is wet or unheated, there is a strong fluctuation in temperatures, thus transmission fluid may lose its properties before its time (change in viscosity, oxidizing, etc.)

Some specialists say that it is possible to “top up” the “old” transmission fluid in case of emergency (when there is a critical fluid shortage). However, it is not recommended to use outdated transmission fluid for complete fluid change. At the same time, it is impossible to say for sure that the use of outdated fluid will necessarily lead to damage or significant reduction in service life of the transmission. However, it is not recommended to constantly use expired lubricants.

How to store transmission fluid

As a rule, the shelf life of transmission fluid or engine oil heavily depends on the type of container in which the lubricant is stored. The best solution is to use the original packing. If you comply with storage conditions, transmission fluids in original containers can be used without doubts during specified service time.

If there is no factory packing, then you have to consider the following solutions:

• Taking into account that UV light can have a negative impact on transmission fluid properties, thus the best solution is a hermetically sealed metal canister. Such solution is perfect for protection against sunlight. However, it is not recommended to store modern fluids (with a large number of additives) in metal canisters far too long, because there are risks of chemical reactions and precipitations. Anyway, in practice, the shelf life of transmission fluids in metal canisters turns out to be the longest.
• Storage containers made of plastic can be used only for short-term storage. The thing is that plastic can go into a chemical reaction with transmission fluid.
• Glass containers are notable for low reliability. The container may crack and glass particles will get mixed with fluid – it will have a negative impact on the fluid properties.

Regardless of the package composition, it is always necessary to check fluid (stored for a long time) before pouring it inside the transmission. The method of fluid inspection is quite simple. It is necessary to take a sheet of white paper, drop some fluid on it, and make it spread on paper. Then, you have to inspect the oil spot. If you notice any embedments, impurities, or particles, then it is better to buy a new fluid. Moreover, pay close attention to the color. Transmission fluids for manual transmissions and dual-clutch transmissions are usually light-colored and translucent, while for automatic transmissions the fluid has reddish or yellowish tints. If the transmission fluid is too light or, on the contrary, is too dark, or if you notice some difference in viscosity, transparency or smell of the lubricant, then it’s better not to take risks and buy a new fluid.

Summary

In view of the above, car owners should pay close attention to expiration dates of fluids used for maintenance of their transmissions. Usually this information is marked on the container (normally 5 years). Moreover, it is also necessary to consider storage conditions of unused fluid. For example, high temperatures can accelerate oxidizing processes, while low temperatures lead to the formation of unnecessary deposits. It is better to store transmission fluid in a dry clean place with temperatures between +10 - +25 ºC.