The short version: this is no 320d M Sport – partly due to the engine and partly due to the standard handling/chassis options. Sometimes, in this business of testing cars, there’s little tangibly different between two models so close in many ways, but the differences are immediately obvious here. Let's start with the engine.
The 318d uses a detuned version of the same 2.0-litre four-cylinder engine found in the 320d, delivering 40bhp less at 148bhp and 59lb ft less torque at 236lb ft, paired with an excellent eight-speed automatic gearbox.
On the road, that equates to perfectly satisfactory performance at everywhere other than the very top end, but it lacks the early, joyful punch of the 320d. Let’s say this: if you didn’t try the 320d, you’d be content with the 318d, but if you did, you’d feel short-changed.
The rear-wheel-drive 3 Series is well known for being the driver's car of choice in the compact saloon segment, and that’s no different here. The 318d in mid-range Sport trim has more flair on this front than the Mercedes C-Class, yet it does feel markedly different from M Sport models (a trim level available with all engines), which come with M Sport suspension and Variable Sport steering.
It was an M Sport version of the 320d that won our five-star accolade, and you can feel the subtle lack of weight and direction in this 'standard' steering set-up. As a result, it feels less engaging in corners, despite the car’s capable rear bias.
What’s gained in driving dynamics is typically lost in ride comfort. Our 318d Sport on 18in wheels had the most passive set-up going. It’s less crashy over bumps than the range-topping M Sport, but it still feels firm, with a case of the mild jitters on poor rural roads.
Inside, the 3 Series’ intuitive functionality and material quality is at least on a par with the Audi A4's and probably just surpasses the C-Class’s. Our test car had the basic 8.8in infotainment screen and analogue instrument cluster, as opposed to the 10.0in screen and digital equivalent found on M Sport trims, yet it felt modern and more than adequate for an executive saloon. The handful of buttons and iDrive remain welcome, despite the broader market’s increasing departure from tactile functions.