It seems that the further Smart stretches its brand philosophy into the mainstream, the less we like the results. Note how we preferred the Forfour with the diminutive 1.1-litre petrol triple to one with the more conventional 1.3-litre four cylinder.
But for this car, the signs are promising, because the diesel is a variant of the four cylinder engine fitted to the new Mercedes A-class, but with one cylinder lopped off.
The 1.5-litre unit features common-rail direct-injection and is available in either a 68bhp version or (as tested here) a 95bhp version with 155lb ft developed at 1800rpm.
Seasoned Smart drivers will instantly recognise the deep, thrummy idle that sounds at odds with the small capacity, and the surging turbo-fed power delivery once moving. Boost arrives smoothly but firmly at around 1600rpm, providing a respectable kick in the back and enough pace to give the Forfour a sprightly feel in traffic.
It’s not quiet, however, and despite the inclusion of a balancer shaft to smooth the triple’s irregular beat, vibrations can be felt through the seat and floor. Those that have bought into the whole Smart experience will no doubt call this a loveable dose of character, but for the rest of us it smacks of poor refinement.