• synthesis of nanofluids by suspending various surfactants–Al 2 O 3 in pure methanol. • surfactant effect on stability and thermophysical properties of MBNF have studied. • more than 180 days stability was found for Al 2 O 3 –methanol–(CTAB) nanofluids. • significant enhancement of thermal conductivity was found. Nanofluids, suspension of nanoparticles, perform better in heat transfer applications due to their excellent thermal properties over conventional heat-transfer fluids. In this study, the stability of Aluminium Oxide (Al 2 O 3 ) methanol nanofluids and their thermophysical properties (thermal conductivity (TC), viscosity, and density) are experimentally investigated. Various surfactants and nanoparticles were suspended into methanol and sonicated to stabilise the suspension at different weight fractions (0.05–0.15 wt%) of the nanoparticles and surfactants. The stability was analysed for the same ratios of different wt.% of nanoparticles and surfactants as a function of time. All the experiments were carried out at a temperature of 298 °K. Nanofluids characterisation, zeta potential and physical observations revealed 0.10 wt% of Al 2 O 3 –methanol with cationic surfactant cetyltrimethylammonium bromide (CTAB) surfactant nanofluids were stable for more than 180 days (6 months). The experimental results found that the TC, viscosity, and density of Al 2 O 3 –methanol nanofluids were all an increasing function of wt.% of nanoparticles. The addition of surfactant into the Al 2 O 3 –methanol nanofluids slightly affects the TC, viscosity, and density. The maximum enhancement of TC with surfactant was found to be 13.7% which was 1.4% lower than without surfactant of Al 2 O 3 –methanol nanofluids. However, the Al 2 O 3 –methanol nanofluids were more stable and had enhanced thermal properties such as (TC, viscosity, and density) over the base fluid. Therefore, the results encourage using these nanofluids in heat transfer applications.