Synthetic lubricating oil and lubricating oil composition

A synthetic lubricating oil comprising an α-olefin (co)polymer defined by the following features (i) to (vi):

• (i) said (co)polymer contains constituent units derived from (a) 1-decene in amounts of 90 to 100% by mol and contains constituent units derived from (b) ethylene in amounts of 0 to 10% by mol,
• (ii) the kinematic viscosity at 100° C. is in the range of 8 to 500 mm2/s,
• (iii) the number-average molecular weight (Mn), as measured by gel permeation chromatography, is in the range of 500 to 15,000,
• (iv) said (co)polymer satisfies the following formulas (I) and (II):
• A≦24.0×Exp(−0.0239×K) (I)
• B≦0.0775×K (II)
• wherein A is a content (%) of a (co)polymer having a molecular weight, as measured by gel permeation chromatography, of not more than 1,000, B is a content (%) of a (co)polymer having a molecular weight of not less than 20,000, and K is a kinematic viscosity (mm2/s) at 100° C.,
• (v) the molecular weight distribution (Mw/Mn) is in the range of 1.1 to 1.8, and
• (vi) the content of unsaturated groups at the end of polymers is in the range of 0.001 to 10%,
• wherein the α-olefin (co)polymer is prepared in the presence of an olefin polymerization catalyst comprising:
• (A) a transition metal compound having a structure represented by the following formula [5] or [6], and
• (B) at least one compound selected from the group consisting of:
• (B-1) an organometallic compound,
• (B-2) an organoaluminum compound,
• (B-3) an organoaluminum oxy-compound, and
• (B-4) a compound which reacts with the compound (A) to form an ion pair;
• wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13 and R14 are each selected from the group consisting of hydrogen, a hydrocarbon group and a silicon-containing hydrocarbon group and may be the same or different, and neighboring substituents among R1 to R14 may be bonded to each other to form a ring;
• M is zirconium, titanium or hafnium;
• Y is a Group 14 atom;
• Q is selected from the group consisting of a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, and each Q may be the same or different;
• n is an integer of 2 or 3;
• and j is an integer of 1 to 4;
• wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R15 and R16 are each selected from the group consisting of a hydrogen atom, a hydrocarbon group and a silicon-containing hydrocarbon group and may be the same or different, and neighboring groups among them may be bonded to each other to form a ring;
• R6 and R11 are the same atoms or groups selected from the group consisting of hydrogen, a hydrocarbon group and a silicon-containing hydrocarbon group and may be bonded to each other to form a ring;
• R7 and R10 are the same atoms or groups selected from the group consisting of hydrogen, a hydrocarbon group and a silicon-containing hydrocarbon group, and may be bonded to each other to form a ring;
• and R6, R7, R10 and R11 are not hydrogen atoms at the same time;
• R15 and R16 may be the same or different;
• M is zirconium, titanium or hafnium;
• Y is carbon or silicon;
• Q is selected from the group consisting of a halogen, a hydrocarbon group, an anionic ligand and a neutral ligand capable of coordination with a lone pair, and each Q may be the same or different;
• and j is an integer of 1 to 4.