| abstract |
Lubricant and functional fluids, and additive concentrates, are composed of a) at least one overbased zinc dialkyldithiophosphate 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 the dithiophosphate is 0.96 or above as determined by 31P nmr, (iii) the integrated 31P nmr spectrum of the dithiophosphate shows less than about 0.25 area percent phosphorus at about 80 ppm, (iv) the integrated 31P nmr spectrum of the dithiophosphate shows essentially no phosphate species at about 5 to about 15 ppm, and (v) the 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. Preferred zinc dithiophosphates are further characterized in that the integrated 31P nmr spectrum of the dithiophosphate shows essentially no phosphorus species at about 95 to about 98 ppm. High thermal and oxidative ability is achieved. |