Lubricating oil composition

Abstract

A lubricating oil composition which exceeds the fuel saving performance of a conventional low viscosity lubricating oil composition, contains (A) a lubricating base oil having a % C_A of 2 or less, adjusted to a 100° C. kinematic viscosity of 1.5 to 4.5 mm²/s and (B) a viscosity index improver including (B1) a poly(meth)acrylate having a weight-average molecular weight of 50,000 or less in an amount of 1 to 10 percent by mass and (B2) a poly(meth)acrylate having a weight-average molecular weight of 100,000 to 250,000 in an amount of 0.1 to 5 percent by mass of the total composition. The composition has a 80° C. high-shear viscosity (Vs: mPa·s) and a 80° C. kinematic viscosity (Vk: mm²/s) ratio (Vs/Vk) of less than 1, a coefficient of traction of 0.02 or less at 40° C., an average speed of 3.0 m/s, a slip ratio of 10%, and a contact pressure of 0.4 GPa.

Description

TECHNICAL FIELD [0001]The present invention relates to lubricating oil compositions, more specifically to those having an enhanced fuel saving performance, suitable for automobile automatic transmissions, manual transmissions, and continuously variable transmissions.BACKGROUND ART [0002]Recently, energy saving in automobiles and construction or agricultural machinery, i.e., fuel saving has become an urgent need in order to deal with environmental issues such as reduction in carbon dioxide emissions, and units such as engines, transmissions, final reduction gears, compressors, or hydraulic power units have been strongly demanded to contribute to energy saving. Consequently, the lubricating oils used in these units are required to be reduced in stir resistance and frictional resistance more than before.[0003]Reduction of the viscosity of a lubricating oil can be pointed out as an effective energy saving means. For example, an automobile automatic transmission or continuously variable ...

AI Technical Summary

Benefits of technology

[0013]The lubricating oil composition of the present invention can reduce resistance to lubrication more than the conventional oils and thus are suitably used in for example automobile manual transmissions, automatic transmissions, continuously variable transmissions or final reduction gears, in particularly suitably continuously variable transmissions so that the composition can contribute to an enhancement in the fuel efficiency of an automobile.

[0014]The present invention will be described in detail below.

[0015]The lubricating base oil referred to as (A) used in the present invention is a lubricating base oil having a % CA of 2 or less and adjusted to have a 100° C. kinematic viscosity of 1.5 to 4.5 mm2/s and may be a mineral lubricating base oil, a synthetic lubricating base oil or a mixture thereof.

[001

Problems solved by technology

However, as described above, the lubricating oil used in these transmissions is also used as a medium for a hydraulic control system and thus would have problems that it would fail to generate suffic

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