In practice, data-driven control and optimization techniques are applied to address problems in engineering systems of which the model is either unavailable or so complicated that a model-based analytic design can be hardly carried. Among them, the extremum seeking (ES) is a popular model-free or data-driven optimization method that has been effectively applied to provide optimal solutions to various industrial control systems. In this article, a new design philosophy, called the model-guided ES, which is a special case of model-guided data-driven (MGDD) optimization, is presented and demonstrated with two successful case studies. In particular, it is shown that, in these two cases, how models of physical systems, even if imperfect or developed in a data-driven way instead of the first-principle based approach, could be integrated together with the conventional ES algorithm to deliver much improved and guaranteed convergence performance and the ultimate bound. It is noted that the first case is for the automotive diesel engine optimization and the second case for the automated regulation of LiDAR detection range. Both cases are successfully validated with experiments.