The present invention relates to a composition containing a lubricant or hydraulic fluid and in an effective amount to improve extreme pressure and anti-wear properties of said lubricant or hydraulic fluid of at least one compound of the formula II ##STR1## R.sup.1, R.sup.2, and R.sup.3 together with the C atom to which they are bound are tert-C.sub.4 -C.sub.14 -alkyl. R.sup.4 is phenyl, --CH.sub.2 --CH.sub.2 --NH.sub.2, --CH.sub.2 CH.sub.2 OH, --CH.sub.2 CH(OH)--CH.sub.2 --OH, tert-C.sub.4 -C.sub.14 alkyl, --(CH.sub.2).sub.2 --S--CH(OH)--CH.sub.2 --S-(tert-C.sub.8 -C.sub.12 alkyl), --CH.sub.2 --COOH, --CH.sub.2 --COO--(i-C.sub.8 H.sub.17), --CH.sub.2 --CO--OH.H.sub.2 N-(tert-C.sub.10 -C.sub.16 -alkyl), --P(S)--[O--(i-C.sub.3 H.sub.7)].sub.2, --P(S)--[O--(i-C.sub.8 H.sub.17)].sub.2, .alpha.-naphthyl, benzothiazolyl, benzimidazolyl, thiazolyl, --CH.sub.2 --CH--(OH)--CH.sub.2 --S--R.sup.10 wherein R.sup.10 is tertiary C.sub.4 -C.sub.14 -alkyl, or R.sup.4 is radical ##STR2## R.sup.1, R.sup.2 and R.sup.3 have the meaning defined above and R.sup.11 is --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 --, o-phenylene, thiadiazol-2,5-ylene or --(CH.sub.2).sub.u --, u being zero to 2.