BMW 525d SE

What is it?

As a result of BMW's engine downsizing programme, the 2.0-litre six cylinder turbodiesel in the 525d has been switched to a four for the 2012 model year 5 Series.

It is a change that has traded two cylinders for twin two-stage turbos and some handy gains in performance, economy and emissions reduction.

Power rises by 13bhp to 215bhp, while the 332lb ft torque peak streams in at 1500rpm to be sustained at that level for another 1000rpm. That's enough to score rapid 7.0sec sprints to 62mph, 149mph and 58.8mpg on the combined cycle - a 20 per cent reduction - and CO2 emissions that fall from 162g/km to 126g/km, an impressive result only diminished by the 119g/km achievement of the 520d EfficientDynamics.

Stop-start is now standard for the eight speed auto as well as the six-speed manual, while BMW's ambitiously named Driving Experience Control simultaneously alters the throttle response, ESP settings, power steering resistance and automatic transmission - shifts to produce Comfort, Sport, Sport+ and a fuel-saving mode called Eco Pro, which lowers the energy demands of the air conditioning and assorted electrical items.

Also new are some minor safety upgrades and electric closing of boot and tailgate, while BMW's already excellent head-up display has been further refined.

What's it like?

An extra 35bhp over the 182bhp 520d may not sound so much, but it's enough to noticeably enliven this 5-series, turning it into a pretty decent sports saloon. If you're laying out for the extra go over the 520d you'll want the variable dampers, too.

They extract more positive feedback from suspension that sometimes feels almost Buick-like in its soft-sprung divorce from the road below. Select Sport or Sport+ however, and the 525 feels lithe and energetic enough to inspire some hard driving.

The 2.0 litre diesel delivers it too, and with impressive smoothness and a stout low-rev surge that the eight-speed auto slickly capitalises on. It's sharp enough to make fingering the paddle shifts a worthwhile exercise too. When you're not in the mood, the 525 settles into an easy high speed cruise, spoiled only be the dull roar around the A pillars that emerges at higher speeds.

Should I buy one?

The 525d manages a very impressive 126g/km as an automatic (the manual is 132g/km), which is good enough to place it in the same 18 per cent benefit-in-kind tax bracket as the 520d EfficientDynamics (it's 19 per cent for the manual). That means the tax penalty for upgrading is not great, and the extra performance makes this a more satisfying driver's car than the 520d ED. If the temptation and the budget are there, this is an engine upgrade that's hard to resist.

BMW 525d SE saloon automatic

Price: £33,610; Top speed: 149mph; 0-62mph: 7.0sec; Economy: 43.5mpg (combined); CO2: 126g/km; Kerb weight: 1645kg; Engine type, cc, installation: 4 cylinder, 16 valve, turbodiesel, 1995cc, longitudinal; Power: 215bhp at 4400rpm; Torque: 332lb ft at 1500-2500rpm; Gearbox: 8-speed automatic