Compared with dry machining, using traditional cutting fluids has some weaknesses, such as environmental pollution, high machining costs, and harmful effects on human health. Internally cooled cutting tools (ICCTs) have been promising, sustainable, health-friendly, and green technologies for turning applications. However, the effects of different types of internal coolant fluids on insert tip temperature (Ttip) have not been investigated for ICCTs. The machining quality of metallic materials and tool life can improve with effective cooling. This study investigates the internal cooling performance of a self-designed internally cooled smart cutting tool (ICSCT) by comparing different heat transfer fluids. Therefore, a conjugate heat transfer (CHT) model was set for a self-designed ICSCT. The CHT simulation was experimentally confirmed using pure water (…developed by Ozturk, E., Yildizli, K., and Saglam, F., 2021, “Investigation on an Innovative Internally Cooled Smart Cutting Tool With the Built-In Cooling-Control System,” Arab. J. Sci. Eng., 46(3), pp. 2397–2411). After that, the effects of flow velocity (Vf) and the inlet temperature of the coolant fluid (Tinlet) alongside different types of glycol-based heat transfer fluids (including pure water) on Ttip were statistically evaluated by the Taguchi method and analysis of the variance (ANOVA). It was found that the most influential factor was the Tinlet at a contribution ratio level of 88.32%. Additionally, according to statistics, Vf and the type of heat transfer fluid were significant. Hence, since no external coolant is used, the designed smart tool can be considered environmentally friendly and health-friendly. In conclusion, glycol-based fluids can be a better choice for internally cooled tool designs owing to their superior features, e.g., corrosion prevention, nontoxicity, and stable heat transfer capability at lower temperatures compared to pure water, although pure water has better thermal properties than the glycol-based fluids (Dynalene Heat Transfer Fluids Technical Datasheets, Cited March 31, 2020).