Based on the available data for the Citroen C4 (2004-08) 3DR Coupe 2.0 HDI 138 VTS, all recorded vehicles are powered by diesel fuel, indicating that the primary fuel type across this model is Diesel with 100% consistency. Additionally, the engine capacity data is only available for vehicles from 1997, which does not directly coincide with the model years specified (2004-08). This suggests that detailed engine capacity information for this particular model may be limited or not captured in the dataset, highlighting a potential area for further data collection.