Diesel Citroen C3s in particular offer outstanding fuel economy of up to 83mpg in official tests, and can top 60mpg in normal driving without too much effort. Citroen C3 1.4 HDi VTR+ Euro 5 [citation needed] The C1 is powered by a 1.0 L three cylinder engine, which has a fuel economy of 61.4 mpg (UK gallons EU method; 4.6 L/100 km EU method; ca 43.4 mpg US with US method) or a 1.4 L four cylinder diesel engine which has a fuel economy of 68.9 mpg (UK gallons EU method; 4.1 L/100 km EU method; ca 48.8 mpg US with US method). What is the fuel economy, Citroen C3 I (Phase I, 2002) 1.4 HDi (68 Hp)? 4.2 l/100 km 56 US mpg 67.26 UK mpg 23.81 km/l: Fuel consumption (economy) - urban : 3Lzzjg.