In this work, the properties of mixtures of 1,2,3,4-tetrahydronaphthalene and trans-decahydronaphthalene were measured. Density and viscosity were measured at temperatures ranging from (293.15 to 373.15) K, and speed of sound was measured at temperatures ranging from (293.15 to 333.15) K. For the mixtures, increasing the mole fraction of 1,2,3,4-tetrahydronaphthalene and decreasing the temperature caused increases in density, speed of sound, bulk modulus, flash point, and surface tension. Mixture viscosities were lower than those of either component. Bulk moduli ranged from (1323 to 2092) MPa over (293.15 to 333.15) K. At room temperature, surface tensions ranged from (30.5 to 35.0) mN.m(-1), and flash points ranged from (328.7 to 343.1) K. The density, speed of sound, and bulk modulus of hydrodepolymerized cellulosic diesel (HDCD) can be matched by mixtures of 1,2,3,4-tetrahydronaphthalene and trans-decahydronaphthalene. The flash point and viscosity of HDCD are higher than those of the mixtures, while its surface tension is lower than those of the mixtures. If combustion is more sensitive to density, speed of sound, and flash point and less sensitive to viscosity, flash point, and surface tension, then a surrogate mixture for HDCD could contain 1,2,3,4tetrahydronaphthalene and trans-decahydronaphthalene.