Automatic transmission fluid composition

Abstract

The present invention provides for a lubricating composition including: a hydrocracker-derived, highly naphthenic, low viscosity index mineral oil; from about 2 wt. % to about 14 wt. % of at least one polymethacrylate polymer; and from about 2 wt. % to about 14 wt. % of a performance additive package. The hydrocracker-derived, highly naphthenic, low viscosity index mineral oil is prepared by: (1) passing a first bottoms portion including not more than about 67 wt. % of a fuels hydrocracker bottoms recycle stream to a dewaxing zone; and (2) passing a second bottoms portion including at least about 33 wt. % of the recycle stream back to the fuels hydrocracker for additional processing; and where the recycle stream has a viscosity at 100.degree. C. of less than about 4.0; (3) contacting the first bottoms portion with a dewaxing catalyst under catalytic dewaxing conditions, where at least a portion of the hydrocracker bottoms is substantially dewaxed; and (4) contacting at least a portion of the substantially dewaxed hydrocracker bottoms with a hydrofinishing catalyst under hydrofinishing conditions, thereby producing a hydrofinished, dewaxed hydrocracker bottoms; and removing from the hydrofinished, dewaxed hydrocracker bottoms at least one light fraction including diesel or jet fuel range material, thereby leaving a heavy fraction including the hydrocracker-derived, highly naphthenic, viscosity index mineral oil having a naphthenes content of at least about 33 wt. %. The lubricating composition has an unsheared kinematic viscosity at 100.degree. C. of at least about 7.3 centistokes; a sheared kinematic viscosity at 100.degree. C. of at least about 6.8 centistokes, where shear is measured by the 20-hour KRL method; and a Brookfield viscosity at -40.degree. C. of no greater than about 10,000 centipoise.