Abstract: Lubricants and additive packages that give exceptional performance as heavy duty gear lubricants are described. Four essential oil-soluble additive components are used in combination, viz., a metal-free sulfur-containing antiwear and/or extreme pressure agent having a copper corrosion test activity of not more than 65; a metal-free phosphorus- and nitrogen-containing antiwear and/or extreme pressure agent; an organic carboxylic acid; and an organic amine. Tests comparing the performance of the invention against a commercial premium API GL-5 gear oil additive package selected as the best available package by a well-known OEM have shown the superiority of the present compositions under a number of test conditions.

Abstract: In a motor vehicle, especially a heavy duty motor vehicle, having a transmission equipped with at least one cone-type synchronizer and an axle or differential gearing, the same lubricant is used for both such mechanisms. The lubricant has a viscosity grade level of from SAE 75W90 to SAE 85W140 and comprises base oil containing at least (i) Mannich base ashless dispersant; (ii) metal-free, sulphur-containing antiwear and/or extreme pressure agent; (iii) metal-free, phosphorus-containing and nitrogen-containing antiwear and/or extreme pressure agent; and (iv) overbased alkali or alkaline earth metal carboxylate, sulphonate or sulphurized phenate having a TBN of at least 145. The lubricant contains at most, if any, 100 ppm of metal as one or more metal-containing additive components other than (iv).