Preventive maintenance means taking measures in advance, before corrective action is needed with regard to the functioning of the equipment. Productive maintenance is when the result of maintenance of equipment is measured (normally in economic terms, e.g., cost-benefit analysis) and the result is positive (i.e., tuning your car regularly will not only prevent damage, it will also save fuel costs). If the savings are superior to the maintenance costs, that is productive maintenance. Together, they are referred to as PPM. PPM is useful as a means for enhancing productivity, minimizing down time, and maximizing efficiency. It involves keeping equipment operating at peak performance levels to help reduce waste.