 The efficiency of older refrigerators can be improved by defrosting (if the unit is manual defrost) and cleaning them regularly, replacing old and worn door seals with new ones, adjusting the thermostat to accommodate the actual contents (a refrigerator needn't be colder than to store drinks and non-perishable items) and also replacing insulation, where applicable.Some sites recommend cleaning condenser coils every month or so on units with coils on the rear, to add life to the coils and not suffer an unnoticeable deterioration in efficiency over an extended period, the unit should be able to ventilate or "breathe" with adequate spaces around the front, back, sides and above the unit.If the refrigerator uses a fan to keep the condenser cool, then this must be cleaned or serviced, at per individual manufactures recommendations.