It's a weighty issue, the four-wheel drive controversy into which Land Rover launches its new Discovery. This vehicle is more than a ton heavier than the typical executive car. That's a lot of material to be wheeling about for the school run, and it shows in the Disco's fuel consumption.
Don't even think about the V8 in this country - its 18.8 mpg is madness with our petrol prices - and even the diesel struggles to return over 27.2 mpg. Greenhouse gases? It certainly emits them, though several comparable off-roaders are worse.
Yet this new Discovery is an excellent vehicle. It can swallow families, venture untroubled through the terrain of a Boys' Own yarn, cruise a motorway or carry furniture. The Discovery has always been a multi-purpose vehicle, and this latest generation, all-new, functions with a civility not seen in the old model. It's also robustly built and well crafted, promising to challenge Toyota's Land Cruiser for durability.
When its design was firmed up four years ago, environmental arguments against 4x4s were less intense than today. As a diesel, it returns fuel consumption comparable to many large cars, and occupies similar road space. And its height increases its effectiveness as a load carrier.
Families may be tempted by its ability to accommodate seven adults in comfort, a feat few vehicles, even most people carriers, can match. With seven travellers, the green objections abate somewhat. There's also a strong case for this machine if you off-road. Part of the reason for its weight is its clever air suspension, its 4x4 transmission and the tough body-chassis unit, all contributing to its ability to ford rivers, climb mountains or indeed mount an urban kerb. One of the Disco's party tricks is its Terrain Response system, which enables you to optimise the suspension's operation merely by rotating a knob.
But in the end, most families acquire these vehicles as classy estates. Not only can they carry vast loads; their lofty vantage point makes journeys more interesting. Plenty buy them because they feel safer too. And it's true that they are better able to absorb severe impacts; but, being tall, off-roaders are prone to topple during extreme manoeuvres. This new Discovery has suspension that counters body lean, as well as a system that lets it corner with unexpected deftness.
All that and a full quotient of airbags make it a pretty safe bet during the unthinkable.
It also makes pleasant long-distance transport. Admittedly, that weight dulls acceleration, but it's brisk enough, and very comfortable. The seats, the classy functionality of the furnishings, the space and the glassy architecture engender a terrific feeling of well-being - provided you can suppress greenhouse gas guilt.
This vehicle - and thousands like it - makes little sense for taking two under-sevens to school. But if you regularly carry large numbers, occasionally off-road, or tow, it's a good option. Even with the handicap of its weight, the new Discovery makes a strong case for itself.
Price: £36,995 (Discovery TDV6 SE)
Max power: 193 bhp
Max torque: 328lb ft
Max speed: 109mph
0-62 mph: 12.2sec
Fuel consumption: 27.2mpg
BMW X5 3.0d SE £35,825
A brisker, sportier drive, more economical, but only five seats; less spacious, not as able off-road.
Volvo XC90 D5 SE £33,085
Again, more economical. Seven seats too, but less spacious, and not as capable off-road.