Abstract : Applying cutting fluid in machining is a typical case, inevitable in grinding, cooling down the tool, prolonging tool life, and gaining a smoother surface. However, the petrol-based cutting fluid may harm the operator, and after being used, residue may damage the environment. This research attempts to reduce those harmful effects using petrol-based cutting fluid by applying a renewable and non-edible one made of Calophyllum Inophyllum, then studying the machined surface's surface integrity in the grinding process. It has compared the results with conventional cutting fluid, called dromus, in grinding of mild steel (St 37 and St 42). The research design used is Taguchi design used to design experiments, followed by optimization analysis. The surface integrity study concerned were (i) hardness alteration, (ii) surface roughness, and (iii) microstructure of the ground surface. So that conclusion is that the newly developed cutting fluid has a better effect in terms of minimum changing of hardness, smoother ground surface, affect changes in the shape of the microstructure denser, and more negligible when using nyamplung as cooling media.