Engineering manufacturing involves the application of different steps to guarantee materials processability and performance in service. This, normally, requires machining, conformation, surface, and heat treatments. A modern concern is related to the process sustainability, the manufacturing capacity to achieve the required properties at low environmental impacts. In this sense, this work evaluated the application of the Polyalkylene Glycol solution (PAG) as a cooling medium of AISI 4140 low alloy steels. The materials were quenched in PAG, water, and Mineral Oil. The medium was compared by the martensite content and hardness distribution results. The results showed a significant advance in the PAG application, which guarantees a higher homogenization on martensite distribution at a low decrease in the hardness profile.