Increasing regulatory demands for fuel consumption and emission reduction have made the investigation of engine thermal behavior during the cold-start phase a key focus in automotive engineering research. The temperature drop of the engine after a shutdown period leads to increased lubricant viscosity and intensified internal friction, which significantly contributes to higher initial fuel consumption. In this study, the effect of a thermal engine encapsulation system on the thermal performance and fuel consumption of the EF7 Plus engine was quantitatively evaluated. To this end, a one-dimensional thermal model was developed in GT-SUITE and validated using experimental data provided by IPCO. By coupling the transient cool-down process with fuel consumption behavior over the standard NEDC driving cycle, the model enabled simultaneous analysis of restart temperature and its impact on engine performance. The results indicate that retaining thermal energy during the soak period increases the initial restart temperature and consequently reduces frictional losses. Both cumulative and instantaneous fuel consumption analyses over the NEDC cycle show that thermal encapsulation can reduce fuel consumption by up to 10% at an ambient temperature of 20°C and up to 11.5% at 5°C. The findings demonstrate the technical and economic feasibility of implementing this technology in commonly used domestic engines.