SAE oil viscosity ratings.
This parameter is key when choosing gear oil for a specific car: viscosity requirements are usually directly indicated in the technical documentation, and you should choose in accordance with it.
In most modern oils, viscosity is indicated by two numbers — for example,
75W-80. The first number, with the W index, describes the low-temperature viscosity — at what temperature the oil thickens so much that it can damage transmission components. You need to pay attention to this number if you plan to operate the car in winter: for example, for a climate with winter temperatures down to -30 °C, brands with values \u200b\u200bnot higher than 75W are recommended. To translate numbers into specific temperature values, there are special tables.
The second number describes the high temperature viscosity, in working order; this is the main performance indicator that determines compatibility with the engine. At the same time, only one digit can be indicated in the characteristics — “winter”; this means that the high temperature viscosity of the oil is the same. However, "purely winter" and "purely summer" oils are not always interchangeable, this, again, should be clarified according to the documentation for the car.
Oils with the following SAE standards are now on the market:
10w,
30w,
50w,
75w,
80w,
90w,
10w-30,
10w-40,
75w-80,
75w-85,
75w-90,
75w-140,
80w-85,
80w-90,
80w-140,
85w-90,
85w-140,
SAE 90,
SAE 140
It is also worth considering that some brands of oils (in particular, for agricultural machinery) can be used both as transmission and motor oils. In such grades, viscosity can be indicated according to the rules of motor oils (these rules are different). One of the signs of such oils is the low "winter" viscosity indicated in the characteristics (well below 70W).
Manufacturer approvals for the gear oil.
Tolerances are the own standards of major automakers, developed taking into account the technical features of individual car models. If the oil meets the tolerance specified in the documentation for the machine, then it takes into account these technical features and is optimally suited for this model.
