We present a detailed study of electro-optical and elastic properties of smectogen octylcyanobiphenyl (8CB) liquid crystal doped with well-dispersed multi-walled carbon nanotubes (MWCNTs). We report new experimental data for the temperature dependence of threshold voltage, dielectric anisotropy, splay elastic constant, and rotational viscosity of MWCNT doped 8CB samples. We have observed that the dielectric permittivity along the long molecular axis and the splay elastic constant decrease with increasing CNT content while the threshold voltage remains the same. Throughout nematic and smectic A phases, the incorporation of CNTs into 8CB has been observed to decrease the dielectric anisotropy, resulting in decreased orientational order. Through optical on and off response time measurements, we have documented that doping 8CB with CNTs results in slower optical relaxation and increased viscosity. Our experimental results directly evidence that CNT doping disturbs the orientational order in 8CB-CNT composites, as previously advocated based on calorimetric data. (C) 2015 Elsevier B.V. All rights reserved.