Tractor hydraulic fluids are multi-application lubricants that are used in transmissions, differentials, final-drive planetary gears, wet-brakes and hydraulic systems of off-highway mobile equipment. Different types of fluids are used in such equipment depending on the design and severity of application. Generally, tractor fluids are designed to meet specific manufacturer requirements.
Some new types of tractors and other off-highway equipment have strict viscometric requirements which standard tractor hydraulic fluids have difficulty in meeting. Moreover, these stricter viscometric requirements may result in seasonal oil changes and even reformulation depending on such seasonal and application requirements.
It would be desirable to have a Summer/Winter, wide temperature range multi-application tractor hydraulic fluid so as to reduce the number of lubricants required on-site to meet different needs and to minimize or avoid oil changes due to seasonal changes.
One example of a tractor hydraulic fluid with a wide operating temperature range is disclosed in U.S. Pat. No. 5,520,832. However, the fluid of that invention does not fully meet the all-season requirements of one of the largest tractor manufacturers, John Deere. In particular, the fluid of that invention does not have sufficient viscosity at high temperature. The fluid of the present invention does fully meet the requirements of John Deere specifications JDM J20C and JDM J20D.