The optimization of result on asset it`s a great concern to financial activity of corporations (private or not). So, they look for conquering and maintainning, through the function price x quality, always the most market share for their services and products. This dissertation presents six methods, and respectives philosophys, used in the replacements politics. The methods are: -Financial mathematics, Costs Equations, Therbogh Methods, Capital Planning. In the eletric sistem this subject is hardly exploited, not less important. Beyond some theoricals aspects we choose a group of diesel motors to apply the methods, and then make results evaluation to introduce the methods in others equipment.