This paper investigates the low-speed performance characteristics of external gear pumps of different sizes under various operating conditions. Experimental studies were conducted on 8 cubic centimeters (cc) and 14 cubic centimeters (cc) displacement pumps to evaluate their behavior across varying speeds and pressures. The key findings indicate that the larger displacement pumps exhibit higher internal leakage and lower volumetric efficiency due to the components’ increased size and surface area. The larger pumps also deliver greater flow at higher speeds, and leakage significantly impacts their volumetric efficiency, particularly at medium pressures and lower operating speeds. Notably, the difference in volumetric efficiency between 8 and 14 cc pumps is most pronounced under these conditions. The torque loss analysis derived from the Stribeck curve reveals that larger pumps experience significantly higher torque losses, especially at elevated pressures of P* = 1. The critical speed findings from Stribeck curve indicate that the smaller pumps are better in elevated pressure applications, offering improved efficiency and durability. The zero-delivery speed of the 14 cc pump exceeds that of the 8 cc pump, with maximum zero-delivery speeds occurring at mid-pressure ranges for both sizes. These findings underscore the advantages of smaller pumps in compactness and efficiency for applications prioritizing low-speed and high-pressure operation. This study emphasizes the importance of selecting suitable pump sizes based on specific application requirements, particularly in electrified mobile machinery, where optimized performance under low-speed conditions is critical.