Bizarrely, this means that despite producing more CO2 - 151g/km compared to the dCi 100's 150g/km - the lower-powered diesel sits in the 16 per cent group, which is three tax brackets lower than the quicker variant. Unfortunately, fuel economy suffers - the 90bhp unit's combined figure of 50.4mpg is 1.9mpg down on the more powerful model.
But the biggest price is paid in performance, with a lack of punch in town, even though the tall sixth gear makes for relaxing cruising. The dCi 90 is also £200 more than the 100bhp car - but it could still cut your company tax bills.