IGCC technology has demonstrated its feasibility, but efficiency and reliability can still be improved. Therefore, an operations map is presented as a tool for optimising gasifier operation. To demonstrate this, two models of entrained flow gasifiers (one simple and the other more complex) are validated with a large set of actual plant periods of operation. The two models are used to build operations maps, which are graphs where the main gasification parameters are related to the degrees of freedom that the operator has. A comparison of the two maps allows one to see the limitations of the simple model and to understand the gasifier’s operation. To construct the maps, a general method for building experimental operations maps from only plant data is required and, thus, needed to be developed. When the method is applied to the gasifier, the tendencies of the maps are the same as those of the model-made maps. Operations maps are, therefore, practical tools that help to operate and diagnose a system (e.g., a gasifier). They allow one to understand how it works, how to optimize its operation, and how to avoid faulty operation which may cause the plant to shut down.