Hydraulic excavators are among the most energy-intensive categories of heavy mobile machinery, characterized by intensive duty cycles, high energy demand, and significant environmental impact. Within the circular economy framework, the evaluation and design of key subsystems should not be limited to conventional performance indicators but should also include life-cycle-oriented criteria, such as durability, remanufacturing potential, resource efficiency, reliability, and user-related economic benefits. This paper proposes an integrated decision-making framework for assessing the circular efficiency of the hydraulic excavator swing drive system by combining engineering performance analysis with the fuzzy Analytic Hierarchy Process (fuzzy AHP). The application of triangular fuzzy numbers enables the modeling of uncertainty and subjectivity in expert judgments, thereby improving the robustness and reliability of criteria weighting. Based on a previously conducted energy-efficiency analysis of a 17-ton hydraulic excavator, two representative design alternatives were selected from a broader set of feasible configurations and evaluated according to hierarchically structured circular economy criteria. The results show that alternative L1 achieves higher overall circular efficiency than alternative L2, mainly due to better performance in energy efficiency, durability, and remanufacturing-related criteria. The proposed fuzzy AHP framework supports sustainable engineering design and component selection in heavy machinery systems.