Real-world MPG: diesel coupes

  • Premium diesel coupes compared
  • 4 Series and E-Class coupes tested
  • Results indicate real-world fuel economy
Words ByEd Callow

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The What Car? True MPG team takes a range of new cars for a thorough road test every week, using special equipment to measure their emissions. Unlike Government data that comes from a laboratory test, our tests show you indicative real-world MPG figures.

The latest models added to the True MPG database are two of the latest executive coupes from BMW and Mercedes-Benz. We tested the new 4 Series and E-Class Coupe in their entry-level diesel guises – both cars claim around 60mpg.

The BMW 420d – fitted with a six-speed manual gearbox – managed a respectable 52.5mpg in our tests, which is a 7.6mpg deficit on its 60.1mpg official figure.

The BMW’s result beats the new Mercedes E-Class Coupe’s – the E220 CDI model with a seven-speed automatic gearbox achieved 49.7mpg in the hands of our technicians, 9.2mpg lower than the claimed economy of 58.9mpg.

Both coupes’ True MPG results are close to their four-door siblings’ figures. The most efficient 320d saloon managed 56.0mpg in our real-world road test, while the E220 CDI saloon (tested before the model’s face-lift) achieved 45.8mpg.

Visit to see the full range of cars we’ve tested, and find out what you really can expect to achieve on UK roads.