Fluid Degradation Counter in CVT transmission

Nowadays, Continuously Variable Transmissions (CVTs) are installed on numerous car models, despite the fact that these transmission solutions in many parameters are inferior to fully automatic transmissions. CVTs have one “mysterious” component named a fluid degradation counter (or just fluid counter), which raises many questions among auto enthusiasts.

Owners of cars equipped with CVTs constantly argue whether it is necessary to reset the oil counter after the oil change. In this article, we will explain the purpose of the fluid counter, its location, and break some myths related to the CVT oil counter.

What is CVT Oil Counter?

The fluid degradation counter is a special algorithm that monitors loads on the transmission and serves to read out the operation data of the transmission and to estimate the fluid condition. To put it simply, the fluid counter is required to inform maintenance specialists about operation conditions to which the CVT was exposed. On the basis of this info, specialists make a decision whether it is necessary to change the transmission fluid or not.

To monitor the CVT fluid condition and fluid counter level in particular drivers can use CVTz50 software

What about fluid Counter Location?

Many drivers often wonder how to find this unusual device. But in fact, all their efforts are doomed to failure, since the counter does not physically exist. It is just a computer algorithm embedded in the ECU of the vehicle, which accumulates a wide range of parameters (real time of operation, shafts rotation, temperature, mileage, speed, etc.) from numerous sensors, analyzes this data, and determines the CVT oil degradation level.

Principle of operation

It is important to understand how the fluid counter calculates the CVT operation data, or rather what is the measurement unit in these calculations. There are different opinions on this question: some people say about kilometers, others claim that the measurements are calculated in hours and minutes, but these assumptions are incorrect. The fluid counter calculates the oil degradation level in arbitrary measurement units. The number of points calculated by the oil counter depends not only on the time of fluid operation, but also on a number of other factors, the main one is the temperature of operation.

Here is how the oil degradation level is calculated on the basis of the operating temperature:

• From 90 to 100 - 1 point
• From 100 to 109 - 2 points
• From 110 to 119 - 4 points
• From 120 to 129 - 6 points
  
• From 130 to 139 - 8 points

Another helpful program to keep track of CVT fluid condition is Torque Pro

Therefore, severe operation conditions which provoke high temperatures (slippages in mud or snow, long-time traffic jams in hot weather, towing of heavy vehicles or trailers, hard accelerations with overheating) result in a greater number of points – bringing closer the time of ATF change. For example, the car manufacturer Nissan recommends changing the fluid in CVT when the fluid counter reaches 60,000 points. At the same time, 60,000 points do not necessarily mean 60,000 kilometers, especially in big cities with huge traffic jams. However, JATCO, the manufacturer of CVT transmissions for Nissan, recommends partial fluid changes every 30,000-40,000 kilometers, and partial fluid changes with the filter replacement every 60,000 km. Thus, it’s up to you who you want to believe (change the fluid in your transmission relying on the fluid counter points or on the mileage).

Is it necessary to reset the counter?

If you change the fluid in CVT on the basis of fluid degradation counter calculations rather than mileage and want to control the residual resource of the CVT fluid, then it is necessary to reset the oil counter during each fluid change. For example, the electronic service manual for Nissan cars literally says the following: “Delete CVT fluid deterioration date with CONSULT-III after changing CVT fluid”.

Part of the online manual for Nissan cars equipped with CVTs

Some specialists claim that if you rely on fluid counter calculations and timely reset it, then you will have the following advantages:

• You’ll be able to monitor operational conditions of your CVT;
• You’ll have full control over fluid change intervals;
• Oil counter data will help to prolong the service life of CVT.

Does the fluid counter affect the oil pressure in the CVT?

Some drivers are convinced that the fluid counter serves not only for the purpose described above, but also directly affects the CVT operation. According to their opinion, when cars equipped with CVTs reach high mileages and the transmission fluid becomes significantly contaminated, the fluid counter sends a signal to adjust the pressure in the transmission for better transmission performance. But unfortunately, that's not the case.

It is true that with time the transmission fluid loses its viscosity, there is even a special unit of viscosity measurement known as Centistokes (cSt). This parameter specifies an acceptable range (not a specific number) of viscosity, and when the cSt value goes out-of-range it is necessary to change the fluid. The fluid viscosity should remain within particular range during the whole period of transmission operation and it can be achieved only by well-timed transmission maintenance (fluid change), and not by means of pressure adjustment.

All in all, the fluid degradation counter is quite a helpful feature for cars equipped with CVTs, which helps a car owner to monitor the transmission fluid condition and to plan timely fluid change. However, it should be noted that the counter performs a purely informative function and it has nothing to do with the pressure regulation.