What's a 'B4' Volvo, you might well ask; and the answer is, it's a diesel-electric 48-volt mild hybrid, designed to slot into the Swedish manufacturer's range of and slowly replace the pure-diesel D3, D4 and D5 engines as it goes. Available at first as the 197hp B4 and 235hp B5, we've tried it here in the mid-sized XC60 SUV.
In the metal
As with the recent changes in other Volvo line-ups, you're looking at familiar fare here. The XC60 Mk2 only launched in 2017 and few car manufacturers, if any, have got their mid-sized SUVs looking quite so 'right' as this, so there have been no visual changes as they're simply not necessary. We've therefore docked it half-a-point in this section for two things and two things alone: one, it'd look even better as an R-Design than as this more sedate Inscription; and two, it doesn't have the biggest boot in the world, as these things go, and as they're bought as family cars primarily then we have to give the Volvo a slight smudge on what would otherwise be its pristine record.
What's changed with this 2.0-litre, four-cylinder turbodiesel variant of XC60 is that its model designation badge on the boot has switched from 'D4' to 'B4'. This modest alphabetic shift is because the old 'Drive-E' diesel lump has been augmented by a 48-volt electrical system, KERS energy recovery and an integrated starter-generator, turning what was once a plain internal-combustion SUV into one that now classifies as a mild hybrid. Like similar systems seen on competitors (see most big Audis nowadays), this recuperates otherwise-lost kinetic energy from the brakes and general momentum, stores it in the battery and then uses said energy to supplement the XC60 B4's acceleration, while similarly powering some ancillaries like the headlights and audio system.
This tech will soon spread to petrol models in the Volvo world and its aim, certainly with the diesels, is to improve fuel economy while simultaneously reducing pollutants such as NOx. What with a fettled automatic gearbox in the mix as well, things look rosy for the new hybrid XC60... until you look at the old D4's stats and see it would do 54mpg (5.2 litres/100km) with 136g/km of CO2. The B4? Well, that records a best of 46.3mpg (6.1 litres/100km) with its lowest emissions rated at 142g/km. Ah.
To be fair to the Volvo, this is because the D4's numbers were done on the old, discredited NEDC regime and the B4's fall under WLTP, so actually the B4 is much more likely to be better on fuel and kinder to the environment. Furthermore, it has had some modest gains in power and torque - up 7hp and 20Nm, to new peaks of 197hp and 420Nm. Again, though, this doesn't seem to have done a lot for the Swede's on-paper numbers: the 0-100km/h time is only a tenth quicker, at 8.3 seconds, while it's 1km/h slower flat out that the D4's 205km/h ceiling.
Nevertheless, you can understand why Volvo has done this. And, in practice, it works so unobtrusively that we kind of wondered if we were in a new car at all. The way the XC60 B4 accelerates, the way it rides and handles, the way the engine sounds; they are all pretty much the same, although we'd perhaps say this 197hp unit sounds just a touch gruffer than we remember the D4 used to. In short, then, Volvo has switched the boot badge and claimed an electrified revolution, but really, it's business as usual for the diesel-powered XC60 SUV.
What you get for your money
The Inscription specification is one of the most expensive on the XC60 (starting at nearly €56,000, and almost €64,000 as this AWD B4), but it suits the SUV's laid-back character better than the sporty R-Design. As standard, all Inscriptions get 19-inch alloys, heated and ventilated electrically adjusted front seats, lots of exterior chrome brightwork and more luxuries, on top of the generous standard trim of a Momentum entry-level model.
A fine SUV, subtly massaged by the addition of 48-volt mild hybrid equipment. Nothing ground-breaking from the Volvo XC60 B4, then, but one of the most likeable, sophisticated and downright excellent family machines has just become a teensy-tiny bit cheaper to run, and easier on the conscience of all eco-warriors.