Gear oil is a type of lubricating oil. Therefore, in addition to having the functions and functions of general lubricating oil, the specific performance of gear oil includes the following characteristics: rheology, load-bearing capacity, thermal oxidation stability, corrosion resistance, emulsion resistance, compatibility with sealing materials, and storage stability.

Bearing capacity includes extreme pressure, wear resistance, and friction improvement. Here, there is a misconception that can easily mislead us, which is the excessive emphasis on good extreme pressure! In fact, extreme pressure does not necessarily mean good load-bearing capacity, as excessive extreme pressure can lead to corrosive wear and deteriorate wear resistance. In my personal opinion, the concept of abrasion resistance can be understood as its name suggests, while extreme pressure resistance is not. Let's take a look at the definition of extreme pressure: the lubricating film bears the load without being squeezed out of the friction surface, resulting in a lack of lubrication ability on the friction surface. Reflected in the detection methods of extreme pressure and wear resistance of gear oil, such as the four ball testing machine, there are indicators of long-term wear and no biting load, as well as simulation of extreme sintering load, that is, extreme dry friction conditions; The OK load of TIMKEN testing machine (GB/T 11144) tends to be closer to the investigation of extreme pressure performance.

In the modern automotive industry, in order to pursue improved fuel economy, the design of the car body is becoming increasingly 'streamlined'. In other words, the airflow passing through the car body and external components is reduced, which directly leads to the deterioration of the cooling conditions of the rear axle of the car; As the power of the car engine increases and the load capacity increases, the size of the transmission gear does not change much, so the specific load on the tooth surface increases. This requires an increase in the thermal load of the vehicle gear oil, which puts higher demands on the thermal oxidation stability of the gear oil. Therefore, the bench test L-60 for thermal oxidation stability has been revised to L-60-1 to evaluate the sedimentation and sludge condition of the gear oil in the test, in order to improve the thermal safety of the oil and the cleanliness of the components. Fortunately, Zibo Huihua Petroleum Additive Company in China has its own unique technology in the thermal oxidation stability of gear oil!

OEM's requirements for the oil change period of vehicle gear oil are becoming increasingly long, and some even require the same lifespan as the vehicle! This increases the compatibility requirements for gear oil and elastic sealing materials, specifically in terms of good rubber swelling properties of gear oil. We know that swelling is the phenomenon of volume expansion of high molecular weight polymers in solvents, which is the main factor affecting the compatibility between gear oil and seals. It is the base oil of the oil, which is more important in synthetic gear oil. At present, the testing methods for the compatibility of oil seals mainly use the D5662 method of ASTM (American Society for Testing and Materials), and the test specimens used are several typical sealing rubbers, nitrile rubber, polyacrylate, and fluororubber. The testing items are elongation, hardness change rate, and volume change rate.