This paper presents a methodology to analyze the cutting fluid effectiveness in mechanical and thermal terms simultaneously using finite element method and experimental work. Cutting fluid plays many roles in metal cutting process. Mechanically-thermally coupled effectiveness of cutting fluids affect to friction coefficient at tool-workpiece interface and cutting temperature and chip control, surface finish, tool wear and form accuracy. Through this study, it can be explained that the critical behavior of cutting fluids will be able to apply optimal environmentally conscious machining process.