Citroen at EVER Monaco in 2006
Diesel or electricity in the C4, gasoline or natural gas in the C3. Unfortunately, the C4 lacks a determining feature which the C3 has: the second tank conection for filling up in the own garage.
Gas is slightly cheaper and more ecologically friendly than a gasoline. So, the C3 has two tank connections. One for gas, one for gasoline.
Electricity is substantially cheaper and produced by sun or wind ecologically friendly. But the C4 HDI Hybrid has no second tank conection to be able to charge the batteries with electricity, best of all from the own photovoltaic roof.