Abstract: The multifunctional lubricant additive compositions of the invention preferably contain a methylene bis(dibutyldithiocarbamate) as an antiwear and extreme pressure additive, a 2,5-dimercapto-1,3,4-thiadiazole derivative as an antioxidant and antiwear additive, a tolutriazole compound as an antioxidant and corrosion inhibitor, a glycerol monooleate as a friction modifier, a calcium sulfonate as a detergent and extreme pressure additive, a zinc dialkyl dithiophosphate as an antiwear and antioxidant additive, a polymethylacrylate as a dispersant, a polyol ester as a carrier and friction modifier, a red dye for leak detection, and optionally, solvent neutral oil and a pour point depressant.

Abstract: An additive system and method of use that significantly extend the service life of petroleum based hydraulic fluids, improve antiwear properties, improve demulsibility, condition and swell seals to prevent leaking, increase oxidation life, improve thermal stability, improve corrosion resistance, improve antifoam characteristics, reduce the acid number of used hydraulic oils, and exhibit improved shelf stability and improved low temperature performance when compared to additive systems previously known, the additive system containing as essential elements a stabilized zinc dialkyldithiophosphate, a substituted sulfolane, an alkyl phenol and an effective amount of a solvent alcohol component selected from C.sub.9 -C.sub.11 or C.sub.12 -C.sub.13 alcohols, or other suitable alcohol blends, with or without other suitable adjunctive solvents such as aromatics or aromatic/ketone blends.