A method for improving deposit control and cleanliness performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil comprises a lubricating oil base stock as a major component, and a mixture of (i) at least one dispersant, and (ii) at least one viscosity modifier, as minor components. The at least one dispersant and the at least one viscosity modifier are present in an amount sufficient to have a critical dispersant thickening ratio of greater than 0.33. The critical dispersant thickening ratio is determined in accordance with the formula:

[00001]$\frac{{\left[G_n\right]}^{*}.Math.\mathrm{dV}.Math.\text{/}.Math.d\left[G_n\right]}{{\left[B_m\right]}^{*}.Math.\mathrm{dV}.Math.\text{/}.Math.d\left[B_m\right]}$

wherein [G.sub.n] is the weight percent of each of n dispersants in the formulated oil, [B.sub.m] is the weight percent of each of m viscosity modifiers in the formulated oil, dV/d[G.sub.n] is the kinematic viscosity (Kv.sub.100) increase of the lubricating oil per the weight percent of each of n dispersants in the formulated oil, and dV/d[B.sub.m] is the kinematic viscosity (Kv.sub.100) increase of the lubricating oil per the weight percent of each of m viscosity modifiers in the formulated oil.

A method for improving deposit control and cleanliness performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil comprises a lubricating oil base stock as a major component, and a mixture of (i) at least one dispersant, and (ii) at least one viscosity modifier, as minor components. The at least one dispersant and the at least one viscosity modifier are present in an amount sufficient to have a critical dispersant thickening ratio of greater than 0.33. The critical dispersant thickening ratio is determined in accordance with the formula:

[00001]$\frac{{\left[G_n\right]}^{*}.Math.\mathrm{dV}.Math.\text{/}.Math.d\left[G_n\right]}{{\left[B_m\right]}^{*}.Math.\mathrm{dV}.Math.\text{/}.Math.d\left[B_m\right]}$

wherein [G.sub.n] is the weight percent of each of n dispersants in the formulated oil, [B.sub.m] is the weight percent of each of m viscosity modifiers in the formulated oil, dV/d[G.sub.n] is the kinematic viscosity (Kv.sub.100) increase of the lubricating oil per the weight percent of each of n dispersants in the formulated oil, and dV/d[B.sub.m] is the kinematic viscosity (Kv.sub.100) increase of the lubricating oil per the weight percent of each of m viscosity modifiers in the formulated oil.

A lubricant composition includes a lubricating base oil, a controlled release friction modifier, a dispersant, a viscosity modifier and a cleanliness booster. The controlled release friction modifier is an ashless, dispersant-stabilized, borated controlled release friction modifier including an ionic tetrahedral borate compound including a cation and a tetrahedral borate anion, wherein the tetrahedral borate anion includes a boron atom having two bidentate di-oxo ligands of C.sub.18 tartrimide.

A lubricant composition includes a lubricating base oil, a controlled release friction modifier, a dispersant, a viscosity modifier and a cleanliness booster. The controlled release friction modifier is an ashless, dispersant-stabilized, borated controlled release friction modifier including an ionic tetrahedral borate compound including a cation and a tetrahedral borate anion, wherein the tetrahedral borate anion includes a boron atom having two bidentate di-oxo ligands of C.sub.18 tartrimide.

The present application concerns a method for separate lubrication of a drive system for a motor vehicle, the system including a compressor and an internal combustion engine including a top end and a bottom end that are coupled together, the method including: lubricating the bottom end with a lubricating composition CL1 having an SAE J300 grade defined by the formula (X)W(Y) in which X represents 0 or 5 and Y represents 4, 8, 12, 16 or 20; lubricating the top end with a lubricating composition CL2 different from the lubricating composition CL1; and lubricating the compressor with a lubricating composition CL2 or with a lubricating composition CL3 different from the lubricating compositions CL1 and CL2.

The present application concerns a method for separate lubrication of a drive system for a motor vehicle, the system including a compressor and an internal combustion engine including a top end and a bottom end that are coupled together, the method including: lubricating the bottom end with a lubricating composition CL1 having an SAE J300 grade defined by the formula (X)W(Y) in which X represents 0 or 5 and Y represents 4, 8, 12, 16 or 20; lubricating the top end with a lubricating composition CL2 different from the lubricating composition CL1; and lubricating the compressor with a lubricating composition CL2 or with a lubricating composition CL3 different from the lubricating compositions CL1 and CL2.

A viscosity index improver containing, in non-ester diluent oil, one or more hydrogenated, functionalized linear block copolymers having at least one block derived from monoalkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and an amount of ester base stock.

A viscosity index improver containing, in non-ester diluent oil, one or more hydrogenated, functionalized linear block copolymers having at least one block derived from monoalkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and an amount of ester base stock.

A viscosity index improver containing, in diluent oil, one or more optionally functionalized linear block copolymers having at least one block derived from alkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and ester base stock and/or at least one star (or radial) polymer, the star polymer being present in an amount such that the c/c.sub.h* value of the star polymer in the concentrate falls within the range of from 0.01 to about 1.6, wherein c is the concentration in mass % of star polymer in the concentrate and c.sub.h* is the critical overlap concentration in mass % for the star polymer in the diluent oil used to form the concentrate.

A viscosity index improver containing, in diluent oil, one or more optionally functionalized linear block copolymers having at least one block derived from alkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and ester base stock and/or at least one star (or radial) polymer, the star polymer being present in an amount such that the c/c.sub.h* value of the star polymer in the concentrate falls within the range of from 0.01 to about 1.6, wherein c is the concentration in mass % of star polymer in the concentrate and c.sub.h* is the critical overlap concentration in mass % for the star polymer in the diluent oil used to form the concentrate.