In this work, the physical properties of binary mixtures of 2,2,4,6,6-pentamethylheptane and 2,2,4,4,6,8,8-heptamethylnonane were measured and compared with those of alcohol-to-jet fuel. 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 343.15) K. At 293.15 K, pure component values for 2,2,4,4,6,8,8-heptamethylnonane of 784.48 kg.m(-3), 3.71 mPa.s, and 1285.8 m.s(-1) for density, viscosity, and speed of sound, respectively, agree with literature values. Similarly for 2,2,4,6,6-pentamethylheptane, the values of 745.21 kg.m(-3), 1.31 mPa.s, and 1203.7 m.s(-1) for density, viscosity, and speed of sound, respectively agree with literature values. Density and mole fraction data were fit to a second-order polynomial at each temperature. Values for bulk modulus ranged from (732 to 1297) MPa over (293.15 to 343.15) K. Viscosity mole fraction data were fit using the three-body McAllister model, whereas the viscosity deviations were fit to a Redlich-Kister type equation. For the mixtures, an increase in mole fraction of 2,2,4,4,6,8,8-heptamethylnonane resulted in an increase in density, viscosity, speed of sound, bulk modulus, surface tension, and flash point. Increases in temperature decreased density, viscosity, speed of sound, and bulk modulus. At room temperature, the surface tension values ranged from (21.4 to 24.0) mN.m(-1), and the flash points ranged from (318.15 to 367.15) K. Comparison of mixture properties with those of an alcohol-to-jet (ATJ) fuel showed that mixtures containing mass fractions of 2,2,4,4,6,8,8-heptamethylnonane around 0.3001 had properties that best matched the ATJ fuel.