Increasingly stringent regulatory demands for fuel consumption and emission reduction have made the investigation of engine thermal behavior during the cold-start phase a key focus of automotive engineering research. The drop in engine temperature after a shutdown period leads to increased lubricant viscosity and intensified internal friction, which significantly contribute 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 against experimental data provided by IPCO. By coupling the transient cool-down process with fuel consumption behavior over the standard New European Driving Cycle (NEDC), the model enabled a simultaneous analysis of the 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 show that thermal encapsulation can reduce fuel consumption by up to 10% at an ambient temperature of 20°C and by up to 11.5% at 5°C. These findings demonstrate the technical and economic feasibility of implementing this technology in widely used domestically produced engines.