A process to prepare a relatively inexpensive utility fluid comprises contacting together ethylene and a coordination-insertion catalyst and, optionally, an alpha-olefin, in a continuously-fed backmixed reactor zone under conditions such that a mixture of a hyperbranched oligomer and a branched oligomer is formed. The hyperbranched oligomer has an average of at least 1.5 methine carbons per oligomer molecule, and at least 40 methine carbons per one-thousand total carbons, and at least 40 percent of the methine carbons is derived from the ethylene, and the average number of carbons per molecule is from 25 to 100, and at least 25 percent of the hyperbranched oligomer molecules has a vinyl group and can be separated from the branched oligomer, which has an average number of carbons per molecule of up to 20. The coordination-insertion catalyst is characterized as having an ethylene/octene reactivity ratio up to 20 and a kinetic chain length up to 20 monomer units.