Overall rating:

Forget about the BMW X1 in this case; it's the new four-cylinder engine we're concerned with here. The 2.0-litre TwinPower Turbo unit will start replacing six-cylinder units in BMWs from the end of the year. If that worries you, oh cylinder-loving rev-mongers, fret not - it's good.

Key Facts

Engine: 2.0-litre four-cylinder turbocharged petrol
Transmission: six-speed manual, four-wheel drive
Body style: five-door compact SUV
Rivals: Six-cylinder petrol engines
CO₂ emissions: 183g/km
Combined economy: 35.8mpg
Top speed: 149mph
0-62mph: 6.1 seconds
Power: 242bhp at 5,000rpm
Torque: 258lb.ft at 1,250rpm

In the Metal:

Imagine the dark grey engine cover with BMW stamped on it that greets you when you lift the bonnet of anything Bavarian Motor Works. There you go. Engines don't look like they used to.

Driving it:

This is a very important engine. It will, eventually, send almost every BMW six-cylinder engine to the great scrapheap in the sky to exchange racing anecdotes, play cards with and smoke CO₂ cigars next to Honda's 2.0-litre VTEC engine and Rover's K-Series.

On paper it looks good: 242bhp from four-cylinders and a single, twin scroll turbocharger that improves low-end response by separating out the cylinders into two pairs, with one pair feeding exhaust gasses into each scroll. It's simpler than twin turbocharging. Compared to a similarly powered six-cylinder engine, torque goes up by 13 percent, but CO₂ down 16 percent. It will become available in lower outputs, too.

On the road, there are no prizes for guessing how the four-cylinder unit behaves. Look at the figures up the page there - this is a strong engine, but it's not one that necessarily thrives on revs. While it heads towards the limiter with characteristic smoothness, to our ears the note is a little gruff; it's clamorous at the top, rather than sonorous. It will grate on the BMW petrol purist.

Still, CO₂ needs must and that. And in any event, history tells us that BMW isn't daft, and will make this thing sing when it needs to - it doesn't really need to in an X1. Fundamentally, it's more flexible than the six-cylinder naturally aspirated alternative because it pulls from lower down.

What you get for your Money:

Because all BMW X1s sold in the UK are diesel, it's unlikely (though not infeasible) you'll get the chance to buy the car we're driving here. Someone at BMW told us, cryptically, that it's an "emotional" engine, when we asked where it would go first. With the new 1 Series due to be unveiled this year, that's a good bet, and it's a certainty to hit the 3- and 5 Series next year.

Worth Noting

Despite our doom mongering about the death of the BMW straight-six, it's actually unlikely to happen any time in the near future. It's true that emissions regulations and the insatiable appetite for good gas mileage (as America puts it) will mean the company will increasingly turn to fewer cylinders and, yes, batteries for power, but we're assured that there'll always be a place for the six-cylinder BMW.

Summary

To be honest we're not particularly fond of the BMW X1 mated with this engine, so we're unconvinced it's worth bothering with over the particularly excellent xDrive23d. However, with our collective desire for more power allied to better fuel economy inexorable, this engine shows that fewer cylinders isn't necessarily an awful idea.