Which? Car is the first UK publication to fully test the new Mercedes-Benz M-class, which is launched in Britain in March 2012.
Controversially, the third-generation M-class uses a diesel engine with only four cylinders – a rarity in the luxury 4×4 class, which is dominated by six-cylinder diesels. The Which? Car tests confirm that the ML250 CDI is more economical than rivals, but suffers somewhat in performance terms.
Economy drive results in 38.2mpg
The reason for using only four cylinders is, says Mercedes-Benz, to boost fuel efficiency. The official combined-cycle fuel economy claim for the new ML250 CDI is 44.8mpg – an impressive figure. The Which? Car lab tests, however, revealed an overall average of rather less, at 38.2mpg.
That’s still economical by full-size 4×4 standards, and beats the figures achieved by Which? Car for six-cylinder rivals like the BMW X5 30d and Volkswagen Touareg 3.0 TDI.
It also means CO2 emissions are kept relatively low for a large 4×4. At 165g/km, you’ll be paying £165 a year in VED tax.
Is it up to the job?
Our testers also asked the question, are four cylinders enough for a luxury 4×4? With a mere 2.1 litres, the ML250 CDI cedes a fair amount of engine capacity to its six-cylinder rivals. The engine’s peak power of 204bhp does, however, match the output of rivals like the Audi Q7 and Volkswagen Touareg in entry-level guise.
With some 2150kg to haul around, the ML250 CDI has just enough performance. And for a four-cylinder diesel, our testers judged it as refined – just not as quiet or smooth as a V6 diesel.
Mercedes-Benz also offers an ML350 CDI model with a 3.0-litre, 258bhp V6 diesel.
£45,375 for four cylinders
The M-class goes on sale in the UK in March 2012 priced from £45,375 for the entry-level ML250 CDI Sport – making it among the most expensive four-cylinder cars on sale in the UK.