"Optimum efficiency" means achieving the best or most effective performance or results with the least amount of wasted resources, time, or effort. Full definition
It keeps the engine operating at optimum efficiency with a band rather than fixed gears. (cnet.com)
It was another move made as part of the retailer's ongoing mission to mold itself for optimum efficiency and profitability in a changing market. (petbusiness.com)
A host of innovative features enhance the car's dynamics and ensure optimum efficiency of the hybrid drive system. (bmwblog.com)