Filling up our Hyundai ix35 crossover recently cost a wallet-wilting £60 for nine gallons of your best foaming diesel. When related to distance covered, it computed to a running average of 45.9mpg over 2000 miles - not too far below the official 48.7mpg figure. But the sought-after 2.0-litre counterpart to our front-wheel drive 1.7-litre promises a theoretical 51.4mpg, albeit with 9g/km more CO2 output.