We report various physical properties such as optical, dielectric, and elastic studies of two high birefringent climate temperature nematic liquid crystal mixtures having similar molecular cores such as quarter phenyl and phenyethnyltolane cores. In both the mixtures, one compound is common, and, in another compound, the lateral group ethyl group is replaced with a methyl group. These mixtures exhibit high birefringence and high elastic constants in comparison to regular liquid crystals. Both the compounds exhibit high birefringence, positive dielectric anisotropy whereas the parallel component shows anomalous temperature dependence. Our results show that with a variation of lateral group, correlation among the cores varies and that reflects in optical and dielectric anisotropies. These studies will be useful in synthesis and exploring appropriate liquid crystals for various display and smart window applications.