This paper studies the impact of a traffic optimisation method called Simplemux, on Quality of Experience (QoE) of Massively Multiplayer Online Role Playing Games (MMORPG). Simplemux allows a number of header-compressed packets of different flows to travel together, sharing the overhead of a common end-to-end tunnel. As a result, significant reductions in terms of bandwidth usage and packet rate can be achieved, but with a trade-off of introducing additional delay and delay variation. In the presented subjective studies we combine artificially created network flows of an MMORPG with traffic of real users, and this mix is sent through an implementation of Simplemux. In this way we simulate a case scenario in which a number of flows share a common network path. Two parameters are modified: the number of active game flows, and the multiplexing period. We examine if the players notice any degradation in their game experience, by comparing two situations: when Simplemux is active or not. Our goal is to investigate whether users’ QoE is degraded by using Simplemux.