An SUV earns its fuel bill in three situations: roads that are not roads, journeys where seven people have to travel together, and occasions where the vehicle is part of the impression.

On a motorway, an SUV does the same job as a saloon and burns half as much again doing it. On a site road in the rain it does a job the saloon cannot do at all.

Worth knowing first

Ground clearance is the point: The reason to take an SUV north is not the badge, it is the clearance and the traction. If the route is motorway all the way, the saloon will cost noticeably less and arrive at the same time.
Seven seats, or seven seats with bags: A seven-seat SUV with the third row up has almost no boot left. For seven people travelling with luggage, a van is the honest answer.
Consumption varies more than you expect: Between a hybrid Haval and a Land Cruiser there is a factor of two in fuel. The figures are on each vehicle's page, and the fare calculator uses them.