The Infiniti M is the Nissan luxury brand's answer to the BMW 5 Series. In many ways it plays the same cards as the Lexus GS - lots of equipment as standard and the option of a hybrid engine. Unlike the Lexus, Infiniti also offers a diesel option. It's not as good to drive as its German rivals, or as well made, but it does offer something a bit different from the mainstream.

There are three engines to choose from - the M37, which has a 315bhp 3.7-litre V6 petrol, the 235bhp 3.0-litre V6 diesel in the M30d or the M35h Hybrid, which has a 302bhp 3.5-litre V6 with a 67bhp electric motor. The M37 is quite fast (0-62mph in 6.2 seconds) when you rev it, but lacks low-end punch, while the diesel is gutsy (0-62mph in 6.9 secs) if a bit rattly and the hybrid is the quickest (0-62mph in 5.5 secs) and most refined of all. However, the standard seven-speed automatic gearbox is slow to react, even in sport mode. The same can be said of the way the M goes round corners. GT models are comfortable but a bit lethargic. You can step up to S spec which brings stiffer springs and four-wheel steering for greater agility, but its 20-inch wheels take the edge off the ride quality. All models are quite quiet, thanks to standard double glazing.

All Infiniti Ms are expensive to run. The M37 claims a poor 27.7mpg and emits a whopping 235g/km of CO2, so doesn't come recommended. The M30d does 37.7mpg but is still very dirty, emitting 199g/km. By comparison, a BMW 530d does 50mpg and 149g/km. That shows you how inefficient the big Infiniti is, and why it would be hard to justify it as a company car. The M35 Hybrid isn't bad though, claiming 40.4mpg and just 162g/km. But then it does cost £47,000. The trouble is, while servicing should be okay - this is a large Nissan, after all - the market is unsure of the Infiniti name and second-hand values will reflect this.

The Infiniti M is a handsome saloon with a bold grille and sleek lines. It certainly stands out next to an Audi A6, BMW 5 Series or Mercedes E-Class, particularly in S spec, which adds huge 20-inch wheels. It's less impressive inside, with plastic and leather trim that doesn't quite match its German rivals. However, it's well equipped, with gadgets like a reversing camera and electrically operated heated and ventilated front seats. Premium models come with sat-nav, a Bose stereo and adaptive cruise control as standard.

At five metres long, the M is a big car and there is lots of room for four adults. However, because of a chunky transmission tunnel, the rear centre seat passenger will be squeezed a bit. The 500-litre boot of the M37 petrol is on a par with rivals like the 5 Series, and the seats fold down too. Beware of the M35 Hybrid version, though - it has a 350-litre boot because the batteries take up some space.

The Infiniti M is extremely safe, thanks to a host of hi-tech gadgets. It's available with adaptive cruise control, brake assist and low-speed collision mitigation, as well as blind spot warning and lane departure warning. In addition, there are six airbags, anti-whiplash front head restraints and traction and stability control. Reliability should be extremely good and, if you do have a problem, we'd expect Infiniti dealers to fix it quickly. One downside is that there are currently only six Infiniti dealers across the country.