Droplet growth rates of droplets suspended in methane gas and supersaturated water and/or n-nonane vapor are experimentally determined. The experiments are performed by applying the nucleation pulse principle using a modified shock tube. The droplets are optically detected using a combination of constant angle Mie scattering and light extinction measurements. From the analysis of the droplet growth rates in the binary systems the diffusion coefficients of water in methane and n-nonane in methane have been determined at two different conditions, being 11 bar and 242 K, and 44 bar and 247 K. The droplet growth rates in the ternary system have been determined at the same two conditions. From the analysis of these experiments it is evident that supersaturated water vapor does not condense onto n-nonane droplets while supersaturated n-nonane vapor does condense onto water droplets. This can be related to the wetting properties of liquid water on liquid n-nonane and vice versa.