When 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 (ICCT) have been a 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. Within effective cooling, machining quality of metallic materials and tool life can improve. Therefore, a conjugate heat transfer (CHT) model for a self-designed internally cooled smart cutting tool (ICSCT) was set. The CHT simulation was experimentally confirmed using pure water. After that, the effects of flow velocity (Vf), 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 effective factor was the Tinlet at a contribution ratio level of 88.32%. Additionally, Vf and the type of heat transfer fluid were found to be significant according to statistics. Hence, since no external coolant is used, the designed smart tool can be counted as being environmentally friendly and health friendly. In conclusion, the 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.