In this study, Carbon nanofiber (CNF), Functionalized Carbon nanofiber (F-CNF), Reduced graphene oxide (rGO), and rGo coated over F-CNF (F-CNF/rGO) were produced using Hummers modified method and chemical reduction methods as well as a hydrothermal technique. All of which were characterized by SEM, TEM, X-ray Photoelectron Spectrometer, and X-ray diffraction. Stability, density, viscosity, thermal and electrical conductivities of the prepared nanofluids (0.04 vol%) were experimentally obtained. Significant enhancements in thermal and electrical conductivity were obtained. F-CNF/rGO (hybrid) nanofluid showed enhanced thermal conductivity and lower electrical conductivity compared to the other prepared nanofluids. Results showed that the hydrothermal F-CNF/rGO (hybrid) nanofluid could result in better heat transfer compared to conventional heat transfer fluids. Moreover, based on the experimental dataset, an accurate model that simulates the thermophysical properties of nanofluids is created by fuzzy logic. A well-fitting is obtained between the experimental results and the fuzzy model. The suggested numbers for fuzzy models rules were 11, 16, 16 and 16 for density, viscosity, thermal conductivity, electrical conductivity models, respectively. Every fuzzy model has been trained for 50 epochs. The MSE of the fuzzy models' outputs are 1.4379e-07, 0.00011349, 1.0709e-05 and 1.9827e-06 density, viscosity, thermal conductivity and electrical conductivity. (C) 2020 Elsevier B.V. All rights reserved.