Thermosyphon is a heat transfer device that effectively manages heat transfer between two solid interfaces by combining the principles of thermal conductivity and phase transition. One of the key features of thermosyphon is that it can convey heat with a very less temperature difference between the heat source and the heat sink. The performance of the thermosyphon is influenced by numerous constraints such as the sonic limit, capillary limit, boiling limit, and entrainment limit. However, it can be improved by selecting proper working fluid(s). In the present work, stainless steel based thermosyphon having outside diameter of 12.8 mm, inner diameter of 11 mm, and a total length of 300 mm is considered. The overall thermal performance of the thermosyphon with different working fluids, i.e., monofluids such as acetone, water, and ethylene glycol, binary fluids such as water with acetone, water with ethylene glycol, and hybrid nanofluids such as water with aluminium oxide and copper oxide are systematically investigated. The filling ratio is kept 65% of the evaporator volume with 6.2 ml of the working fluid. The experiments are carried out in the vertical position with thermal loads ranging from 10 to 100 watts. These findings revealed that Up-to 20 Watt of heat input, acetone performs better compared to the other fluids. At 10 Watt of heat input, the acetone gives 21 % more thermal conductivity compare to hybrid nanofluid, and 80 % more thermal conductivity compare to water. Beyond 20 Watt of heat inputs, the hybrid nanofluid performs better. At 100 Watt of heat input, hybrid nanofluid give 17 % more thermal conductivity compare to water and 62.5 % more thermal conductivity compare to acetone.