From a thermodynamic perspective, roughly speaking fuel based engines convert the flow of heat from a high temperature heat bath to a low temperature heat bath

From a thermodynamic perspective, roughly speaking fuel based engines convert the flow of heat from a high temperature heat bath to a low temperature heat bath into work. The higher the difference between the temperatures the more work can be extracted. It would seem to me that in theory the vehicle surface area could be used as the colder heat bath for improved efficiency. I am not claiming any actionable specific device or configuration design to improve the efficiency though!