Low ash lubricating oil compositions

An additive concentrate suitable for addition to oil-based lubricants and functional fluid compositions, said additive concentrate comprising a minor amount of liquid inert diluent and a major amount of the following combination of components:

• a) at least one overbased zinc dialkyl dithiophosphate characterized in that (i) each of the alkyl groups is a primary alkyl group containing from 6 to 10 carbon atoms,.(ii) the overbased to neutral ratio of said dithiophosphate is 0.96 or above as determined by .sup.31 P nmr, (iii) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows less than about 0.25 area percent phosphorus at about 80 ppm, (iv) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows essentially no phosphate species at about 5 to about 15 ppm, and (v) said dithiophosphate exhibits a copper weight loss in ASTM Test Method D2619 of 0.70 maximum;
• b) at least one hindered phenolic antioxidant or at least one aromatic secondary amine antioxidant;
• and
• c) at least one overbased alkaline earth metal sulfurized alkyl phenate having a TBN as determined by ASTM Test Method D2896 of at least 200 or at least one alkaline earth metal alkyl aromatic sulfonate.

An oil-based lubricant or functional fluid composition which comprises a major portion of at least one base oil of lubrication viscosity and:

• (a) about 0.2 to about 2 wt. % of at least one overbased zinc dialkyl dithiophosphate characterized in that (i) each of the alkyl groups is primary alkyl group containing from 6 to 10 carbon atoms, (ii) the overbased to neutral ratio of said dithiophosphate is 0.96 or above as determined by .sup.31 P nmr, (iii) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows less than about 0.25 area percent phosphorus at about 80 ppm, (iv) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows essentially no phosphate species at about 5 to about 15 ppm, and (v) said dithiophosphate exhibits a copper weight loss in ASTM Test Method D2619 of 0.70 maximum;
• (b) about 0.01 to about 2.5 wt. % of a combination of (i) at least one oil-soluble hindered phenolic antioxidant and (ii) at least one oil-soluble aromatic secondary amine antioxidant in proportions such that there are about 3 to 14 parts by weight of said phenolic antioxidant per part by weight of said amine antioxidant;
• and
• (c) about 0.001 to about 2.0 wt. % of a combination of (i) at least one said overbased alkaline earth metal sulfurized alkyl phenate and (ii) at least one said alkaline earth metal alkyl aromatic sulfonate in proportions such that there are about 3 to about 3.5 pats by weight of said phenate per part by weight of said sulfonate.

An additive concentrate suitable for addition to oil-based lubricants and functional fluid compositions, said additive concentrate comprising a minor amount of liquid inert diluent and:

• (a) about 25 to about 70% of at least one overbased zinc dialkyl dithiophosphate characterized in that (i) each of the alkyl groups is primary alkyl group containing from 6 to 10 carbon atoms, (ii) the overbased to neutral ratio of said dithiophosphate is 0.96 or above as determined by .sup.31 P nmr, (iii) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows less than about 0.25 area percent phosphorus at about 80 ppm, (iv) the integrated .sup.31 P nmr spectrum of said dithiophosphate shows essentially no phosphate species at about 5 to 15 ppm, and (v) said dithiophosphate exhibits a copper weight loss in ASTM Test Method D2619 of 0.70 maximum;
• (b) about 12 to about 48 wt. % of a combination of (i) at least one oil-soluble hindered phenolic antioxidant and (ii) at least one oil-soluble aromatic secondary amine antioxidant in proportions such that there are about 3 to 14 parts by weight of said phenolic antioxidant per part by weight of said amine antioxidant;
• and
• (c) about 2.3 to about 9.5 wt. % of a combination of (i) at least one said overbased alkaline earth metal sulfurized alkyl phenate and (ii) at least one said alkaline earth metal alkyl aromatic sulfonate in proportions such that there are about 3 to about 3.5 pats by weight of said phenate per part by weight of said sulfonate.