The distinction rests on chemical definition: if the product is a mixture of isomers or homologs with no single compound constituting the predominant fraction in a way that makes it chemically defined, it falls under 3817. A product that is essentially a single, chemically defined compound—even if minor impurities are present—belongs in Chapter 29. Importers should have compositional analysis available to support classification.

The primary end uses are as base fluids for synthetic lubricants and heat-transfer oils, and as intermediates in the manufacture of linear alkylbenzene sulfonate (LAS) detergents. Refiners, lubricant blenders, and surfactant manufacturers are the main commercial buyers, and shipment volumes often track production schedules in those downstream industries.