Olefin isomerization process

A process of isomerizing at least one linear .alpha.-olefin having from about 14 to about 20 carbon atoms, said process comprising contacting said linear .alpha.-olefin with a catalytic quantity of a catalyst consisting essentially of supported or unsupported nonmetallic sulfonic or perfluorosulfonic acid resin catalyst, at a pressure in the range of from 0 to 400 bars and (a) at a temperature in the range of from 90.degree. to 120.degree. C. and at a catalyst concentration in the range of about 10,000 to about 100,000 parts by weight of catalyst per million parts of olefin starting material when the catalyst is a particulate sulfonic acid ion-exchange resin, (b) at a temperature in the range of from 120.degree. to 180.degree. C. and at a catalyst concentration in the range of about 100 to about 25,000 parts by weight of catalyst per million parts of olefin starting material when the catalyst is a perfluorinated ion-exchange polymer having pendant sulfonic acid groups, or (c) at a temperature in the range of from 60.degree. to 120.degree. C. and at a catalyst concentration in the range of about 100 to about 50,000 parts by weight of catalyst per million parts of olefin starting material when the catalyst is a perfluorinated ion-exchange polymer having pendant sulfonic acid groups either (i) supported on a carrier or (ii) in a porous microcomposite with a carrier, to thereby isomerize the linear .alpha.-olefin to form a trisubstituted olefin and only internal olefins having their double bond no closer to any terminal position than the 3-position in an olefinic oil product mixture having a viscosity at 100.degree. C. of no more than about 1.6 cSt, a viscosity at 40.degree. C. of no more than about 39 cSt, and a pour point of -5.degree. C. or lower.