An elastic analogue model that describes the equilibrium between opposed jets have been validated for Confined Impinging Jets (CIJs) mixers using fluids with the same physical properties for a wide range of flow rate ratios between the opposed jets. Using this model as a design tool CUs can efficiently mix fluids at non-unitary flow rate ratios. This paper extends the experimental and numerical characterization of the flow in CUs for fluids with a viscosity ratio of 1:2 for a range of flow rate ratio up to 1:2. Experimental characterization is made with Planar Laser Induced Fluorescence, and numerical study is based on 3D CFD simulations of the CIJs. Experimental and numerical results coincide and show that the balance of kinetic energy rate of the opposed jets plays the key role on the jets impingement point positioning, although viscosity also has an impact on this. The elastic analogue model makes a good prediction of the impingement point position of the opposed jets. This paper shows that the operation at a flow regime with high mixing efficiency, a chaotic flow regime, depends on impinging the opposed jets at the CIJs mixing chamber axis and operating at Reynolds number larger than 125 for the lower Reynolds number jet. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.