NOVELTY - Converting bio mass-derived streams of hydrocarbon diols into fuel additive, comprises: (a) providing biomass-derived feedstream comprising 5-6C hydrocarbon diols; (b) contacting feedstream with first catalyst in a reactor, where the contacting results in an acidic condensation reaction that converts at least a portion of feedstream to condensation products; and (c) reducing at least a portion of remaining hydroxy groups on the obtained condensation products by combining the condensation products with second catalyst in presence of hydrogen to produce water and a liquid hydrocarbon mixture.    USE - The method is useful for converting bio mass-derived streams of hydrocarbon diols into a fuel additive, which is useful for a liquid hydrocarbon fuel (claimed).    ADVANTAGE - The process: provides the liquid hydrocarbon mixture having increased miscibility in liquid hydrocarbon fuels; provides the liquid hydrocarbon fuel exhibiting increased cetane number and/or decreased emissions of environmental pollutants during combustion (all claimed); does not require hydrogen for oxygen removal, hence it is simple and cost effective; can be performed at low temperatures; and minimizes the production of undesirable cyclic secondary products, as compared to conventional processes.    DETAILED DESCRIPTION - Converting bio mass-derived streams of hydrocarbon diols into a fuel additive, comprises: (a) providing a biomass-derived feedstream comprising 5-6C hydrocarbon diols; (b) contacting the feedstream with a first catalyst in a reactor, where the contacting results in an acidic condensation reaction that converts at least a portion of the feedstream to condensation products, and the condensation products comprise at least 10C and at least one ether functional group; and (c) reducing at least a portion of the remaining hydroxy groups on the obtained condensation products by combining the condensation products with a second catalyst in the presence of hydrogen to produce water and a liquid hydrocarbon mixture suitable for use as an additive for a liquid hydrocarbon fuel, where the liquid hydrocarbon mixture has increased miscibility in liquid hydrocarbon fuels as a result of step (c).