<p>The present research focus is to examine the thermal conductivity (TC) enhancement of water–ethylene glycol base heat transfer fluid through the inclusion of copper oxide (CuO), titanium dioxide (TiO₂), magnesium oxide (MgO) and multi-walled carbon nanotubes (MWCNT) nanoparticles (NP), forming four kinds of hybrid nanofluids for experimentation. In addition, six dihybrid nanofluids were generated for TC experimentation. They were water–ethylene glycol with CuO and TiO₂, water–ethylene glycol with CuO and MgO, water–ethylene glycol with CuO and MWCNT, water–ethylene glycol with TiO₂ and MgO, water–ethylene glycol with TiO₂ and MWCNT, and water–ethylene glycol with MgO and MWCNT. All the nanofluids were prepared by two-step chemical method. The NP concentration was 0.2, 0.4, 0.6, 0.8, 1 and 1.2% in water–ethylene glycol for all the above-mentioned nanofluids. The TC (TC) measurements were taken at temperatures 27, 28, 29, 30, 31 and 32 ºC with the aid of KD2 pro TC analyzer (accuracy ± 0.005 w m⁻¹&#xa0;°C). In case of hybrid nanofluids, the MgO with water–ethylene glycol resulted better thermal performance at the chosen temperatures due to the tetrahedron lattice structure of MgO nanoparticles followed by TiO₂ with water–ethylene glycol. The average TC enhancement was 18.2% and 13.8% for MgO with water–ethylene glycol and TiO₂ with water–ethylene glycol, respectively. The agglomeration of CuO and large l/d of MWCNT resulted in poor TC of nanofluids. The inclusion of CuO and TiO₂ in water–ethylene glycol recorded 10.2% rise in TC as an average. The average TC increase was 4.8% only with CuO and MWCNT in water–ethylene glycol. The respective TC increase with CuO and MgO, MgO and MWCNT, and TiO₂ and MWCNT in water–ethylene glycol is 6.4%, 7.1% and 7.8%. Overall, the TiO₂ and MgO nanoparticles attributed better TC rise of 19.4% average at selected temperature and concentration.</p>