Process to prepare a heat transfer oil

A process to prepare a heat transfer oil, comprising: a. dewaxing a substantially paraffinic wax feed by hydroisomerization dewaxing using a shape selective intermediate pore size molecular sieve under hydroisomerization conditions including a defined hydrogen to feed ratio, whereby a lubricating base oil is produced, b. selecting one or more fractions of the lubricating base oil having: i. a low pour point, ii. greater than 10 weight percent and less than 70 weight percent total molecules with cycloparaffinic functionality, wherein the one or more fractions have at least 31.2 wt % 1-unsaturations by FIMS, and iii. a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15; and c. blending the one or more fractions of the lubricating base oil with less than 0.2 wt % antifoam agent to prepare the heat transfer oil of a defined ISO viscosity grade.