Transmission Fluid Compositions for Hybrid and Electric Vehicle Applications

A transmission fluid composition comprising:

• a major amount of a lubricating oil basestock;
• and
• a minor amount of an additive package comprising:
• (i) a mixture comprising two or more compounds of structures (I):
• wherein groups R1, R2 and R3 are independently alkyl groups having 1 to 18 carbon atoms or alkyl groups having 1 to 18 carbon atoms where the alkyl chain is interrupted by a thioether linkage, provided that, in the mixture (i), at least some of groups R1, R2 and R3 are alkyl groups having 1 to 18 carbon atoms in which the alkyl chain is interrupted by a thioether linkage;
• (ii) one or more compounds of structures (II):
• wherein groups R4 and R7 are independently alkyl groups having 1 to 12 carbon atoms and R5 and R6 are independently alkyl linkages having 2 to 12 carbon atoms;
• (iii) a detergent comprising calcium salicylate;
• and
• (iv) a basic nitrogen-containing ashless dispersant comprising one or more compounds of structure (III):
• wherein:
• R8 and R9 are each independently a hydrocarbon group made by the metallocene-catalyzed polymerization of an α-olefin feedstock comprising 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-octadecene, or mixtures thereof;
• each R10 is independently hydrogen, an acetyl moiety, or a moiety formed by reaction between ethylene carbonate and >N—R10;
• and
• x is from 1 to 10 and is the same for all molecules of structure (III) or is an average of all molecules of structure (III) in a mixture of molecules of structure (III).