A novel composition is disclosed that is particularly useful as a lubricant viscosity index improver. The composition comprises branched branched C.sub.30 -C.sub.10000 hydrocarbons that have a branch ratio of less than 0.19 and viscosity at 100.degree. C. between 725 CS and 15,000 cS. The novel compositions comprise the product of the oligomerization of C.sub.6 to C.sub.20 alpha-olefin feedstock, or mixtures thereof, under oligomerization conditions at a temperature between -20.degree. C. and +90.degree. C. in contact with a reduced valence state Group VIB metal catalyst on porous support. The compositions have viscosities at 100.degree. C. between 725 cS and 15,000 cS. Using the foregoing compositions in admixture with mineral oil and synthetic lubricants provides novel lubricant blends that show an elevated viscosity index. The mixtures also show an increased stability to shear stress at high temperature with all blends notable by exhibiting Newtonian flow.