It has now been discovered that oligomers of C6- C20 alpha-olefins, such as 1-decene, with branch ratios below 0.19 and high viscosity indices (HVI) can be functionalized to provide unique phosphite derivatives. Functionalized polyalpha-olefin lubricants compositions are prepared with superior properties by adding functionalized organophosphites to the olefinic bond of HVI-PAO. The invention encompasses a process for the preparation of lubricant range hydrocarbons containing phosphonate functional groups, comprising; reacting olefinic C20+ polyalpha-olefin oligomers having a branch ratio of less than 0.19 and phosphite ester in a mixture with peroxide catalyst at elevated temperature whereby phosphite ester adduct of said polyalpha-olefin is formed; separating said reaction mixture products and recovering said adduct.