Aromatic compounds are alkylated with C.sub.20 -C.sub.1300 olefinic oligomers using an acidic alkylation catalyst to produce alkylated aromatic products, usually alkylaromatic hydrocarbons. The olefinic oligomers used as alkylating agents are prepared from 1-alkene oligomerization in contact with reduced metal oxide catalyst, preferably reduced chromium oxide on a silica support. The alkylated aromatic hydrocarbons retain the unique features of the alkylating olefinic oligomer and exhibit high viscosity index and low pour point. If the alkylation is carried out under certain combinations of conditions, especially using a Lewis acid catalysts such as aluminum trichloride and at higher temperatures, the alkyl portion of the product will undergo isomerization. The alkylaromatic compositions show improved thermal stability and are useful as lubricant basestocks and additives for improved antiwear properties, antioxidant and other properties.