The present contribution deals with the thermomechanical fatigue behaviour (TMF) of the cast iron material GJV450 (CGI450, compacted graphite iron). This type of cast iron offers interesting possibilities for engine manufacturers for fulfilling the raised requirements for mechanically and thermally loaded components. It is typically used for cylinder heads, where the material properties of aluminium or gray cast iron are not sufficient for withstanding the high thermal and mechanical loading of modern engines. A detailed characterisation concerning thermal and mechanical effects under thermomechanical fatigue does not only indicate possible limitations in using this material, but gives also explanations of the failure behaviour. As of today, sophisticated components like cylinder heads are designed with the help of sophisticated simulation methods e.g. the Finite Element Method (FEM) making use of various advanced constitutive models for describing the material and lifetime behaviour. Hence, if the local loading conditions can be calculated, it is possible to compute lifetime values to assess the durability of components. In many cases, the constitutive parameters are estimated from quasi-static or isothermal tests, which results often in gross inaccuracies. Therefore, a further focus of this work is the application of material models and lifetime calculation methods on the results from TMF investigations. It turns out that the use of conventional empirical methods for lifetime estimation is not always successful. As a result from those investigations, an alternative method is proposed for estimating the lifetime of components based on maximum temperature and a constraint factor. With this method, some light can be shed on discrepancies encountered between conventional simulation results and experimental results from TMF tests. The method is easily integrated into the design stage of the product development process.