Viscosity (SAE)
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).
Compliance
General standards that this brand of oil complies with.
The most popular standard used for gear oils for manual transmissions is API. It provides the following classes:
— API GL-1. Oils with a relatively simple composition and a minimum of additives. Designed for relatively simple working conditions, they are intended for bevel and worm gears, as well as gearboxes for trucks and agricultural machinery that do not have synchronizers.
— API GL-2. Worm gear oils designed for moderate conditions. They have an increased amount of additives compared to GL-1, they are used mainly in agricultural machinery.
API GL-3. Oils intended mainly for trucks (except models with hypoid gear). Designed for moderate conditions, contain various additives (up to 2.7%).
— API GL-4. The most popular variety of "mechanical" oils. Suitable for all conditions, can be used in bevel and hypoid gears, synchronized and non-synchronized gearboxes, in all classes of vehicles (although the specific purpose of different brands is different). Contains up to 4% additives.
— API GL-5. Oils for severe conditions and gears operating under heavy loads — primarily hypoid, with a large axle offset. Contains up to 6.5% additives. Many grades are suitable for manual transmissions with synchronizers and/or limited slip differentials (this should be explicitly stated in the oil specifications).
— API GL-6. Oils specially formulated for hypo
...id gears operating at high speeds, heavy loads and/or shock loads. Differs from GL-5 in an even greater content of extreme pressure additives.
— API MT-1. Specialized oils for heavy equipment with non-synchronized manual transmissions — primarily "trucks" and buses. Generally similar to GL-5, but more resistant to high temperatures.
In addition, manual transmission oils may be labeled according to the SAE standard, developed by the association of the same name. Note that in this case we are not talking about the total viscosity according to SAE (see the relevant paragraph), but about special standards. The most common is compliance with the SAE J2360 standard. It states that the oil "exceeds the requirements of API GL-5" (see above) and is intended for use in hypoid gears operating under increased loads (including high speed or high traction at low speed) and with numerous surfaces, sliding contact.
In turn, automatic transmission oils use their own standards. The most popular is Dexron, developed by General Motors; historically, this is the first standard; for a long time, most automakers in the US and Europe were guided by it. Here are the options found in modern brands of "automatic" oils:
— Dexron II / IID / IIE. The earliest Dexron standard in use today. The original Dexron II (sample of 1972) in its pure form is practically never found today, because some components of such oils accelerate the corrosion of gearbox parts. Dexron IID formulations contain an anti-corrosion additive, but these oils are hygroscopic. Dexron IIE, in turn, eliminates this shortcoming, and also significantly improves efficiency at low temperatures.
— Dexron III / IIIF / IIIG / IIIH. The original Dexron III (also known as Dexron IIIF) was introduced in 1993 as a more advanced alternative to the Dexron II, while also being backwards compatible (with a few exceptions). At the same time, oils of this standard showed insufficiently high durability and wear resistance, which led to the appearance of additional modifications. So, Dexron IIIG (1997) is distinguished by high efficiency at low temperatures, and Dexron IIIH, which replaced it in 2003, has increased oxidation resistance, improved extreme pressure properties and longer service life. All Dexron III licenses expired in 2006; oils of these standards continue to be produced, but without the control of General Motors.
— DexronVI. A standard that appeared in 2005 as the successor to Dexron III; since 2006, only this standard has been officially supported by General Motors. Provides a lower initial oil viscosity than previous standards, which has a positive effect on the overall quality of the transmission, and also has stricter wear viscosity reduction tolerances and, accordingly, better extreme pressure characteristics.
Another popular "automatic" standard developed and maintained by Ford is called Mercon. It is less diverse in terms of the number of specifications: the most common variants include the original Mercon, developed back in 1987, Mercon IV (1997), Mercon V (2001) and Mercon LV (2009). Each subsequent standard is more perfect and backwards compatible with the previous ones. Somewhat apart in this row is the Mercon SP, designed for the Ford 6R gearbox used in engines with a longitudinal arrangement. It is also worth noting that the requirements of this standard are similar to the requirements of Dexron, and Mercon-compliant oils usually also have Dexron certification.
Somewhat less common is the marking of "automatic" oils according to the JASO standardused by Japanese automakers. Japanese-made automatic transmissions have their own characteristics and specific requirements for oils, which is why a separate standard is applied for them. When choosing such an oil, you should focus primarily on the requirements specified in the documentation for the car.Manufacturers approvals
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.
