An oxidatively stable, biodegradable lubricant composition, comprising:
- (A) at least one hydrogenated polyisoprene prepared by polymerizing isoprene such that polyisoprene is obtained wherein there are from 4 to 1000 isoprene units wherein the polyisoprene prior to hydrogenation has the formula ##STR51## wherein n is the number of isoprene units and hydrogenating the polyisoprene to obtain a hydrogenated polyisoprene containing a residual olefinic unsaturation of not more than 10 percent based upon the unsaturation content prior to hydrogenation and;
- (B) at least one performance additive selected from the group consisting of
- (1) an alkyl phenol of the formula ##STR52## wherein R.sup.3 is an alkyl group containing from 1 up to about 24 carbon atoms and a is an integer of from 1 up to 5;
- (2) an ether of the formula ##STR53## wherein R.sup.80 is an alkyl group containing from one up to about 12 carbon atoms, R.sup.3 is an alkyl group containing from one up to about 24 carbon atoms and a is an integer of from one up to 5;
- or ##STR54## wherein R.sup.75 is an aliphatic group containing from one up to 8 carbon atoms, n and m are independently integers of from zero up to 100 with the proviso that n and m are not both zero;
- (3) a mixture of a mono- or di-substituted glyceride of the formula:
- ##STR55## wherein R.sup.81 and R.sup.82 are hydrocarbyl groups independently containing from about 8 up to about 24 carbon atoms;
- (4) a phosphorus-sulfur derivative of the formula ##STR56## wherein R.sup.43 and R.sup.44 are independently hydrocarbyl groups containing from about 3 to about 20 carbon atoms and B is ##STR57## a mixture of ##STR58## in a ketone:alcohol weight ratio of from 1:0.10-0.50;
- (5) a benzotriazole of the formula ##STR59## wherein R.sup.4 is hydrogen or an alkyl group of 1 up to about 24 carbon atoms;
- (6) a phosphorous amine salt;
- (7) a trihydrocarbyl phosphorothionate;
- (8) an aromatic amine of the formula ##STR60## wherein R.sup.12 is ##STR61## and R.sup.13 and R.sup.14 are independently a hydrogen or an alkyl group containing from 1 up to about 23 carbon atoms;
- (9) a zinc salt of the formula ##STR62## wherein R.sup.43 and R.sup.44 are independently hydrocarbyl groups containing from about 3 to 20 carbon atoms;
- (10) an ester having pour point depressant properties characterized by low-temperature modifying properties of an ester of a carboxy-containing interpolymer, said interpolymer having a reduced specific viscosity of from about 0.05 to about 2 and being derived from at least two monomers, one of said monomers being a low molecular weight aliphatic olefin, styrene or a substituted styrene wherein the substituent is a hydrocarbyl group containing from 1 up to about 18 carbon atoms, and the other of said monomers being an alpha, beta-unsaturated aliphatic acid, anhydride or ester thereof, said ester being substantially free of titratable acidity and being characterized by the presence within its polymeric structure of pendant polar groups which are derived from the carboxy groups of said ester:
- (a) a relatively high molecular weight carboxylic ester group, said carboxylic ester group having at least 8 aliphatic carbon atoms in the ester radical, optionally
- (b) a relatively low molecular weight carboxylic ester group having no more than 7 aliphatic carbon atoms in the ester radical, wherein the molar ratio of (a):(b) of the pour point depressant when (b) is present is (1-20):1, and optionally
- (c) a carbonyl-amino group derived from an amino compound having one primary or secondary amino group, wherein the molar ratio of (a):(b):(c) of the pour point depressant when (b) and (c) are present is (50-100):(5-50):(0.1-15);
- (11) a hydrogenated block copolymer comprising a normal block copolymer or a random block copolymer, said normal block copolymer made from a vinyl substituted aromatic and an aliphatic conjugated diene, said normal block copolymer having from two to about five polymer blocks with at least one polymer block of said vinyl substituted aromatic and at least one polymer block of said aliphatic conjugated diene, said random block copolymer made from vinyl substituted aromatic and aliphatic conjugated diene monomers, the total amount of said vinyl substituted aromatic blocks in said block copolymer being in the range of from about 20 percent to about 70 percent by weight and the total amount of said diene blocks in said block copolymer being in the range of from about 30 percent to about 80 percent by weight;
- the number average molecular weight of said normal block copolymer and said random block copolymer being in the range of about 5,000 to about 1,000,000;
- and
- (12) an acrylate polymer of the formula ##STR63## wherein R.sup.9 is hydrogen or a lower alkyl group containing from 1 to about 4 carbon atoms, R.sup.10 is a mixture of alkyl, cycloalkyl or aromatic groups containing from about 1 to about 24 carbon atoms, and x is an integer providing a weight average molecular weight (Mw) to the acrylate polymer of about 5,000 to about 1,000,000.