Abstract: A clean performing gear oil for use in transmission oils and axle lubricants is provided. The gear oil having a Brookfield Viscosity at -12.degree. C. ranging from about 1,000 to about 150,000 cP, comprises a base oil having a kinematic viscosity at 100.degree. C. ranging from about 4.0 to about 41.0 cSt. Combined with the base oil is preferably a dispersant pour point depressant and/or a dispersant viscosity index improver. In a further preferred embodiment, the gear oil is essentially devoid of carboxylic-type ashless dispersants (e.g., succinimide dispersants) and Mannich base dispersants, thus realizing a cost saving over conventional gear oils which are used as transmission and axle lubricants. Functionalized polymethylacrylates (PMA) are disclosed as agents that improve the properties of the gear oil and allow for the omission of conventional dispersants.

Abstract: The present invention relates to a clean gear boron-free gear additive employing a boron-free ashless dispersant, a sulfur source and a phosphorus source. More particularly, the preferred boron-free ashless dispersant is a hydrocarbyl succinimide. This additive composition when blended with a suitable base oil meets MT-1 and MIL-PRF-2105E requirements without the need for boron. MT-1 is a requirement for a clean gear manual transmission oil. MIL-PRF-2105E is a requirement for a rear axle oil.

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 .sup.31 P nmr, (iii) the integrated .sup.31 P nmr spectrum of the dithiophosphate shows less than about 0.25 area percent phosphorus at about 80 ppm, (iv) the integrated .sup.31 P 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.