Trying to justify why you need a petrol-engined Audi Q7 is a fool's errand. Never try to do this. You will end up either sounding spoiled, snobbish or, worst of all, like an engineer. Is there really any excuse for this quite enormous luxury 4x4, especially when a 3.6-litre FSI engine is slotted into that vast engine bay?

Let's look at the financial case first. There isn't much of a financial case when compared to the 3.0-litre diesel Q7. The diesel is not only cheaper to buy but also massively cheaper to run. Justify the 3.6 FSI to yourself instead by thinking of the children. Opt for the diesel engine and you'll be forcing them to breathe all manner of carcinogenic particulates. Yes, this 3.6-litre six-cylinder might chug out 304g/km of carbon dioxide but as any biologist will tell you, this is the very gas that trees breathe. At this juncture you can probably tell that I'm struggling to justify this vehicle and it's probably best to come clean. I'd buy the Q7 3.6 FSI over the diesel because it's faster. There. I said it.

Packing 278bhp does that for this big Audi, and that's fully 48bhp more than the diesel model in a car that carries significantly less weight in the nose. Where the diesel feels like a big plodder, the 3.6-litre Q7 turns into a corner more crisply. The front suspension is less concerned with isolating the ironmongery in the nose and can concentrate on soaking up imperfections in the road. It feels a very different and hugely more enjoyable car to steer through a set of corners.

The price for this is a fuel consumption figure of 22.2mpg on the combined cycle. I ran a long-term Q7 3.6 FSI, this vehicle's big brother, and could never get anywhere near Audi's quoted economy figures, even if I drove the thing as if the luggage bay was packed with nitro glycerine, so expect around 19mpg from the 3.6-litre car in 'real world' driving conditions.

Is it possible to drive this car without feeling a degree of guilt? Even if I had more money, I don't think the nagging sense of profligacy would really evaporate. Only if you're lugging a family around and you really need the seven seats can you approach the Q7 with any sense of justification but even then, there are plenty of other vehicles that will do the job with a little less excess. In the final reckoning, the only way to really square driving this car is by treating it as an unashamed indulgence and vow to make amends elsewhere in your life.

"The Q7 3.6 FSI isn't an easy car to justify. Sometimes, however, life can seem too short for tedious justification"

Despite the lighter engine and weight-saving aluminium parts, this behemoth still tips the scales at over 2,200kg, so it needs all the horsepower it can get if it's to make dignified progress. While it lacks the step-off ability of the big 4.2 V8 and the midRange of the 3.0-litre diesel, the 3.6-litre FSI nevertheless feels nimble and plenty quick enough in most scenarios to keep even a well-driven GTI honest. It'll get to 60mph in just 8.2 seconds and run onto a top speed of 142mph which, in a vehicle of this size, takes a lot of stopping. Fortunately the Q7's brakes are commensurately super-sized.

All Q7s are equipped as standard with quattro permanent four-wheel drive. The Torsen centre differential directs power to all four wheels, on-road and off-road, which means fast-reacting power to whichever wheel can best deploy it and excellent lateral stability - the prerequisites for optimum driving dynamics and safety. The driver benefits - also thanks to virtually balanced axle load distribution - from even better agility and steering precision that remains practically free of torque steer.

The chassis of the Audi Q7 comprises numerous aluminium components - independent wheel suspension with double wishbones at the front and rear - and excels with its all-round qualities. Steel spring suspension and twin-tube shock absorbers are designed for sporty driving and superior comfort, even off-road. The tilted position of the rear spring and shock absorber unit reduces overall height and creates more room at the rear.

With a length of 5,086mm and a wheelbase of 3,002mm, the Q7 isn't the most nimble rock hopper, but it does feature variable ground clearance (from 180 to 240mm), hill descent assist and an off-road mode whereby the ESP stability control system backs off to allow for loose surfaces. There's also a trailer stabilisation system which reduces the risk of fishtailing via targeted brake intervention.

Three versions are offered, all with a six-speed tiptronic automatic gearbox. You'll need £38,225 to secure the entry level model, although Audi predicts that most customers will be tempted to splash a little more cash for the £40,725 SE variant. At the top of the Range is the £41,625 S line model. Whether or not you see the Q7 as a big step forward for Audi really rather depends on your view of big 4x4s. I always liked the Allroad, a pragmatic vehicle that was more competent than most would require off road and had a reassuringly car-like feel on the tarmac. The air suspension system could turn your suave estate car into a mud plugger in a matter of seconds without the negative social connotations of larger 4x4s. The Allroad was a clever distillation of Audi's brand image - cool, pragmatic, well built and ever so slightly self effacing.

It doesn't have the versatility of the Q7 though. Audi claims 28 seating and loading configurations are available in this car and the seats in the second row are adjustable for fore/aft movement. This allows Audi to not only lay claim to the most generous second row legroom in the class but also - with the second row slid forward and the rear folded - to also pinch first prize for luggage capacity, a huge 775 litres.

The Audi Q7 3.6 FSI requires you to be brutally honest about what you want a luxury 4x4 to do. The benefits this car brings over the diesel model are entirely hedonistic but at the same time, not quite so extreme as the 4.2-litre car. It's a vanishingly tiny strip of a sliver of a slice of a market niche but no less delicious for it.

TOP 3 Q7 DEALS

The results below show the top Q7 deals on buyacar

	Audi Q7 3.6 FSI Quattro SE 5dr Tip Auto Estate
	ETR	Mthly £663	Saving £2,907	Price £38,518
	Audi Q7 3.6 FSI Quattro S Line 5dr Tip Auto Estate
	ETR	Mthly £658	Saving £2,907	Price £38,518
	Audi Q7 3.6 FSI Quattro 5dr Tip Auto Estate
	ETR	Mthly £621	Saving £2,707	Price £36,218

typical 9.59% APR

PCP finance quote over 48 months,  10,000 miles pa,  deposit of £1000