Steels for machine manufacturing can be hardened through thermal treatments. In the quenching treatment is possible to use different substances to improve mechanical properties, in particular hardness and probably the wear resistance. As quenching media, the water, water and salt solutions, polymer solutions, vegetable oils and mineral oils are commonly used. In this work, vegetable oils (vegetable blended, soybean, canola and sunflower) and mineral oil (10W30) were used as an alternative of quenching media to study the performance of the hardness and the microstructures obtained. The quenching treatment was carried out involving heating at temperature of 850? C and keeping inside electric furnace for 50 minutes to achieve homogeneity in the internal structure. The quenched was carried out at room temperature using each vegetable and mineral oils. The results showed that use of vegetable oils is a good alternative as a tempering substance. The results showed that vegetable oils have a better performance than mineral oil, as they allow to reach hardness above 40 HRC and generate high strength and toughness microstructures. Among vegetable oils, Canola oil allowed the highest hardness and the microstructure with the best presence of bainite.