Unfortunately, car manufacturers in general and particularly the Germans have been fitting ever bigger wheels with ever lower profile tyres to their cars. The Mazda 6 Skyactiv D 140 SE-L Nav is okay on 17-inch wheels with 55 profile tyres. And the Volvo S60 D4 with the new 2.0 litre 182PS DriveE engine on 17-inch wheels with 50 profile tyres is all right. But for the best fuel economy (I got 63mpg over 8000 miles), go for a BMW 320dED, which comes on 16-inch wheels with 60 profile tyres as standard. All of these have between 380 and 400Nm torque, so plenty of grunt as well.