Onto part two of our route, then, and more inviting and open Welsh A-roads. With batteries now mostly depleted, the fuel efficiency of the cars depends mostly on how drivable they are, and how effective their hybrid systems are at scavenging energy. Pretty soon, both trip computers are indicating considerably less impressive economy numbers: low 30s from the Volvo, and high 20s from the BMW. But we’re driving the cars quite hard, and asking them to cover greater distance than may be routinely required of them. High-mileage drivers take note: you’re probably still better off in a conventional diesel than either of these cars.
A fulfilling motoring life isn’t all about miles to the gallon, though. Twisting mountain roads will quickly remind you of that, if you let them. While both of our SUVs take to them with greater vigour and involvement than a typical diesel 4x4, it’s the Volvo that shines more brightly on them – completing something of a rout for its maker.
While neither of our cars has the telling muscle of a proper performance 4x4, the XC90 has something almost as good: a real wallop of tractive urge on tap between about 40 and 70mph, right where you need it. Both cars have sporty modes for their suspension, powertrain and steering systems, and both cars allow you to manually select your own gears. However, the Volvo takes off more quickly than the BMW when everything is set just-so – quick enough to shade almost any diesel SUV I can think of – while the X5 can feel a little inconsistent and strained when overtaking.
The Volvo’s ride and handling shade the BMW’s by an even wider margin. It corners with greater poise and natural balance than the BMW and rides much more fluently. All this is helped by it having the more weighty, feelsome and incisive steering. The Volvo is the more softly sprung car, so it rolls a touch harder and feels slightly underdamped occasionally, but it has distinguishing ride comfort.
The BMW handles gamely when harried, just as you’d expect it to, but its steering is too slow around dead-centre, too muted on feedback and just a bit too imprecise and inconsistent at times to inspire the confidence you need to tackle a twisting road with much gusto in a really big car. The X5’s ride seems needlessly firm: hyperactive over camber changes and through ruts, and slightly coarse with it – at a guess, at least partly as a result of the runflat tyres our test car came fitted with. All in all, it feels like a car struggling against its dynamic limitations next to one that’s much more at one with them.
It leaves us with a singular conclusion. Before this test, I wasn’t sure that the financial case for a petrol-electric luxury SUV could stack up against a diesel – but it can. I didn’t expect the XC90 T8 to be capable of driver appeal on the one hand and rational appeal on the other: to deliver on performance, handling, refinement and creditable economy.