The thermodynamic and fluid-dynamic properties associated with the injectant jet significantly influence its fluid dynamic characteristics. In most of the earlier studies on the behavior of liquid jet at high pressure and supercritical environment, the liquid jet is often injected at subcritical initial temperature. In the present study, the effect of variation in the fluid and flow properties of the injecting jet on the nature of instabilities and mixing behavior is investigated. The fluid properties of the injected jet are varied by preheating. High-speed imaging techniques are used to capture the jet behavior. To gain further insight into the instability nature of the jet, linear instability analysis was performed. Dynamic mode decomposition analysis was applied to the obtained high-speed images to extract and understand the relevant dynamic features. © 2020 Author(s).