Nakamura, Y., Horikoshi, M., TAKEI, Y., Onishi, T. et al., "Development of Next Generation Gear Oil for Heavy Duty Vehicles," SAE Technical Paper 2017-01-0890, 2017, doi:10.4271/2017-01-0890.
Heavy duty vehicles take a large role in providing global logistics. It is required to have both high durability and reduced CO2 from the viewpoint of global environment conservation. Therefore lubricating oils for transmission and axle/differential gear box are required to have excellent protection and longer drain intervals. However, it is also necessary that the gear oil maintain suitable friction performance for the synchronizers of the transmission. Even with such good performance, both transmission and axle/differential gear box lubricants must balance cost and performance, in particular in the Asian market. The development of gear oil additives for high reliability gear oil must consider the available base oils in various regions as the additive is a global product. In many cases general long drain gear oils for heavy duty vehicles use the group III or IV base oils, but it is desirable to use the group I/II base oils in terms of cost and availability. The main key technologies for group I/II oil-based gear oils are the additive components chosen and the formulation balance to achieve anti-wear optimum protection and extreme pressure conditions. This paper describes development focused on the evaluation of anti-wear and extreme pressure components using tests, the improvement of the extreme pressure properties, the provision of corrosion inhibition on the gear tooth surface, and the maintaining of friction properties for the synchronizers in the transmission. As a result, the lubricant gives durability and long drain interval performance, even blended in the group I/II base oils.