Our cars: Citroen DS3 - May

No matter how enthusiastically I drive my DS3, its trip computer always tells me I'm averaging at least 36mpg. According to the official figures I should be getting 42.2mpg, but given how notoriously difficult it is to match these laboratory figures in the real-world – and that I drive mostly around town – I'm quite happy with the 36mpg the computer tells me I'm getting.

To get a more scientific verdict, I gave my car to our fuel economy expert, Peter de Nayer. With more than 30 years' experience measuring the real-world fuel consumption of cars using sophisticated fuel meters, I knew he'd be able to tell me exactly what my DS3 was capable of.

On the What Car? route – our own test designed to replicate moderate real-world driving – the Citroen clocked an impressive 40.4mpg, according to Peter's equipment. That's despite me leaving the bike rack in place, which created more aerodynamic drag at speed.

Sadly, the results also revealed that my car's trip computer is prone to exaggerating. So when it says I'm getting 36.0mpg around town, I'm actually getting 32.4mpg. I'll be taking it extra easy until my next pay day, then!