This research is driven by the desire to improve efficiency of the Subsonic Aerodynamic Research Laboratory (SARL) at the Wright-Patterson Air Force Base, Dayton, OH. Previous research indicates a 30% loss of pressure occurring at the exit of the tunnel. A 60:1 scaled model of the SARL tunnel and four different diffuser geometries were tested to determine the most efficient diffuser for reducing overall losses. Experimental results were compared against computational simulation analysis results obtained using the same diffuser models by King (2012) to validate the computational results. Four cases were studied experimentally using a Kiel Probe and Netscanner pressure scanner. The inlet velocity profile entering the 60:1 scaled diffuser models was a fully developed velocity profile with an average velocity of 60 m/s and a center velocity of 72.5 m/s Total pressure losses downstream of the diffuser models were measured to determine the most efficient geometry to reduce pressure losses and decrease operational cost of the SARL system. Both the experimental and CFD results show that the “3.5 Base + Flat + Conical” diffuser results in the least total pressure loss throughout the system. The experimental results indicate a 37% percent reduction in the total pressure losses while the CFD results gave a 45% reduction in the total pressure losses in comparison to the pressure losses measured for the existing “7.5 base” diffuser on the small scale. Implementing this diffuser model could improve the overall efficiency of the full scale SARL tunnel by 11%