Low-viscosity lubricating oil and functional fluid compositions

A low-viscosity engine lubricating oil composition, said composition being characterized by a phosphorus content of about 0.01% to about 0.1% by weight and comprising:

• a major amount of an oil having a kinematic viscosity of up to about 4 cST at 100.degree. C.;
• and a minor antiwear amount of
• (A) a compound represented by the formula ##STR23## wherein in Formula (A-VII), R.sup.1 and R.sup.2 are independently hydrocarbyl groups, and X is O or S, and
• (B) a phosphorus compound.

A process for making an engine lubricating oil composition characterized by enhanced antiwear properties, comprising:

• mixing an oil having a kinematic viscosity of up to about 4 cST at 100.degree. C.;
• and
• (A) a compound represented by the formula
• R.sup.1 R.sup.2 N--C(X)S--(CR.sup.3 R.sup.4).sub.a Z (A-I)
• wherein in Formula (A-I), R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen or hydrocarbyl groups, provided that at least one of R.sup.1 and R.sup.2 is a hydrocarbyl group;
• X is O or S;
• a is zero, 1 or 2;
• and Z is a hydrocarbyl group, a hetero group, a hydroxy hydrocarbyl group, an activating group, or a --(S).sub.b C(X)NR.sup.1 R.sup.2 group wherein b is zero, 1 or 2;
• provide that when a is 2, Z is an activating group;
• and when a is zero, Z can be an ammonium, amine or metal cation;
• said oil composition being characterized by a phosphorus content of about 0.01% to about 0.1% by weight.

A process for making an engine lubricating oil composition characterized by enhanced antiwear properties, comprising:

• mixing an oil having a kinematic viscosity of up to about 4 cST at 100.degree. C.;
• and
• (A) a compound represented by the formula ##STR25## wherein in Formula (A-VII), R.sup.1 and R.sup.2 are independently hydrocarbyl groups, and X is O or S;
• said oil composition being characterized by a phosphorus content of about 0.01% to about 0.1% by weight.