Torque is a concept many motoring enthusiasts discuss but few understand. Ask the next bar room expert to define the difference between torque and power and you'll usually be greeted by a stumbling mix of hearsay and GCSE physics. If you need to understand what torque is all about, forget the formulae and get behind the wheel of a Volkswagen Touareg TDI.

Three mainstream diesel versions of the Touareg exist. The first, the 2.5 TDI, uses a five-cylinder 174bhp 2.5-litre turbodiesel engine and costs from £29,880. The second, the V6 TDI, uses a 3.2-litre turbo diesel powerplant developing some 241PS and costs from £32,640. The third bolts two 2.5 TDI engines together to form a V10 cylinder 5.0-litre powerplant of quite stupendous pulling power. Mind you, you'll be expected to pay almost twice the price for the privilege. The 313PS V10 TDI costs £55,200 although a determined bit of haggling may see some movement on the latter figure. If you find yourself wanting even more power, there is an R50 range-topping unit that employs a 345bhp version of the V10 diesel. All the TDI powerplants feature Volkswagen's Pump-Duse unit injector system.

Given that the 2.5-litre engine is effectively half the 5.0-litre unit, most of the basic technology is the same. Neither engine offers the common-rail architecture many manufacturers crow about, but given the results Volkswagen have achieved, you won't feel hard done by. Sales figures show the 2.5-litre TDI to be the most popular model in the entire Touareg line up and it returns some excellent figures. Although it's not quite got the mumbo of a 3.0-litre BMW X5 diesel, it's a good deal cheaper and feels a more modern package. It will accelerate to 60mph in 12.2 seconds and run on to a top speed of 114mph on the standard steel spring suspension. Plump for the optional air suspension and top speed falls to 111mph. A combined fuel economy figure of 28.8mpg is fair return for such a huge vehicle. Both standard and SE versions of this model can be ordered, then there's the option of the menacing Altitude with its bigger wheels and body styling accessories or the R50 with even bigger wheels and more extrovert styling accessories.

The 241PS V6 TDI has more than enough engine for the task of dealing with Mercedes, Land Rover and BMW rivals. Suddenly the asking price of around £32,000 doesn't seem quite such an obstacle. The SE variant is pitched at £36,040. It's also an agreeably muscular engine, generating some 369lb/ft of torque. It's broadly similar to the unit found beneath the bonnet of the Phaeton V6 TDI limousine, except for the fact that the Touareg's installation has been tuned to offer more in the way of low down grunt. This means that the Volkswagen is adept at towing or hauling up steep inclines.

"The Touareg V10 TDI is a true leviathan amongst cars"

The overall fuel consumption figure of 25.9mpg is a reasonable showing given the Touareg's enormous all-up weight, and the acceleration to 60mph of 9.7 seconds is also firmly on the right side of acceptable. Top speed is quoted as 125mph, so motorway cruising shouldn't see the engine being flogged too hard. The emissions of 294g/km are hardly stellar but if you're buying this sort of vehicle, that's not likely to be a prime criterion. The engine is a good deal more advanced than either of its other diesel siblings, using an advanced piezo electric injector capable of making up to four fuel injections per cycle.

As for the V10 TDI, well perhaps this diesel should be called The Diesel Engine. It's a monster. This 313PS 5.0-litre V10 TDI turbodiesel generates 542lb/ft of torque. What does that mean in the real world A V8 turbodiesel Range Rover develops 472lb/ft, whilst a diesel BMW X5 manages 369. Pitiful! Lamborghini Murcielago - a limp wristed 479lb/ft. A Ferrari Enzo hawks up 484lb/ft. The Touareg V10 TDI is a true leviathan amongst cars and what that makes the 345bhp R50 is anyone's guess.

So what's the car like in the metal? In a word, big. At 170cm high it's not lacking in road presence. The range-topping V10 TDI sits a couple of centimetres higher still on its air suspension, the other models relying on more conventional steel springs. Unless, that is, you want to hit the options list.

The current car is a good deal better looking, adopting the latest Volkswagen family face with the bold grille and also adding some rather sleek headlamp units that are fluted along the bottom edge. This means new front wings and bumper assemblies to make everything fit, so this hasn't been a low budget exercise. Revised door mirrors also feature as do new lower profile rear light clusters, with a beefier spoiler and exhaust pipes also evident if you know what you're looking for. The interior styling is pleasantly restrained, the materials quality is class leading and the look and feel is much like the opulent Phaeton.

On the road, the Touareg can't quite match the class-leading BMW X5. It comes close, though, and is a little tauter than a Range Rover and a touch keener than a Mercedes M-class. The Volkswagen has slightly more lateral roll in corners and there's that bit more side to side 'wobbly head syndrome' that BMW has worked so hard to exorcise. The V10 TDI is monstrously muscular, despatching the sprint to 60mph in 7.6 seconds yet will return an average of 23mpg - a decent return for a car that tips the scales at around 2,500kg. It's off road that the Touareg plays its trump card, especially when equipped with air suspension. Permanent four wheel drive and a low ratio gearbox are taken for granted, but factor in selectable front and rear differential locks, hill start and descent assist and very short front and rear overhangs and the Touareg becomes an awesomely capable tool. There's also ABSPlus, a system which can cut braking distances by as much as 20 per cent on muddy surfaces. With low range engaged, the Touareg can drag itself up a 45-degree slope with 35 degrees of sideways lean. The V10's torque is always a bonus, but the light weight of the five-cylinder TDI engine makes it particular nimble on downhill stretches.

Touareg diesels represent respectively the most popular and most powerful models in the line up and given the choice available it seems an act of reckless folly to plump for the petrol model over this trio of oil burners. Oh, and in case you were wondering, torque is defined as a measure of how much a force acting on an object causes that object to rotate (or Force x Moment Arm). One suspects you'll find the concept of a Touareg TDI a good deal easier to understand.

TOP 5 TOUAREG DEALS

The results below show the top TOUAREG deals on buyacar

	Volkswagen Touareg 2.5 TDI DPF 5dr Off Road
	ETR	Mthly £463	Saving £2,580	Price £27,425
	Volkswagen Touareg 2.5 TDI DPF 5dr Tip Auto Off Road
	ETR	Mthly £486	Saving £2,720	Price £28,685
	Volkswagen Touareg 2.5 TDI DPF Altitude 5dr Off Road
	ETR	Mthly £575	Saving £4,545	Price £31,660
	Volkswagen Touareg 2.5 TDI DPF Altitude 5dr Tip Auto Off Road
	ETR	Mthly £598	Saving £4,689	Price £32,956
	Volkswagen Touareg 5.0 V10 TDI DPF SE 5dr Tip Auto Off Road
	ETR	Mthly £953	Saving £6,457	Price £48,868

typical 9.75% APR

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