A method for improving the lubricating properties of a water-based fluid used in metalworking operations comprising the step of adding to said water-based fluid a lubricating additive having the generic structural formula: ##STR8## wherein R1 is an alkyl, cycloalkyl, aryl, alkaryl or aralkyl group having from 1 to 34 carbon atoms; R2, R3 and R4 are independent alkylene groups having from 2 to 30 c