Chevron U.s.a. Inc.

Gene E. Robinson

John a. Zakarian

Gene E Robinson

John A Zakarian

The invention includes a tractor hydraulic fluid composition containing a major amount of a base oil mixture. The base oil mixture includes a first mineral oil having a kinematic viscosity at 100.degree. C. of at least about 4.0 centistokes and a second mineral oil having a kinematic viscosity at 100.degree. C. of at least about 7.0 centistokes. The tractor hydraulic fluid composition also contains a first polymethacrylate viscosity index improver and a second polymethacrylate viscosity index improver having a lower shear stability index than the first polymethacrylate viscosity index improver. The tractor hydraulic fluid composition has an unsheared kinematic viscosity at 100.degree. C. of at least about 9.1 centistokes, a sheared kinematic viscosity at 100.degree. C. of at least about 7.1 centistokes, and an unsheared kinematic viscosity at -40.degree. C. of not more than about 20,000 centipoise.

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Concord, CA, United States of America

Gene E Robinson