The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 30, 1999
Filed:
Dec. 30, 1997
John A Zakarian, Kensington, CA (US);
Gene E Robinson, Concord, CA (US);
Chevron U.S.A. Inc., San Francisco, CA (US);
Abstract
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.