Road Test: Mercedes-Benz E Class E250 CDI SE 5dr 7G-Tronic

Another mental marker has popped into my head - 500Nm of torque. That's 369 lb ft, but 500 is easier to remember and it's a number the high-end Germans seem to cluster their diesels around.

A quick glance at the stats in the back of the book reveals that the 3.0-litre V6 TDI in the Audi A4 makes 500Nm of torque. The BMW 330d makes 500Nm too - a 3.0-litre straight six diesel. And so does this new diesel engine in the E-Class, the E250 CDI.

This is a remarkable engine. It's only a four, that's the impressive bit - it's the same 2,143cc unit fitted to the single-turbo C200 CDI and C220 CDI. But in this application, it has twin sequential turbochargers running at full puff. Good.

The lag-free slug of torque is deep and fine from tickover, and slings this relatively big car forward at an eye-widening rate. It's almost bizarre. You would never expect it, given the quite loud, dull drone of the four-pot - it's almost as if a silent 5.0-litre V8 has been slung in the boot to help out.

It dispatches 0-62mph in 8.2 seconds and returns 47.1mpg on the combined cycle. That's an impressive combo and makes this the engine of choice in the new E-Class - it's clean too at 154g/km, so road tax is only £150 a year.

Oh, and one more mental marker for you: specific torque output is 233.2Nm per litre. If you can think of an engine that beats it, send us a postcard.