From £51,0158

Has the plug-in hybrid sporting executive saloon finally come of age?

Since the designation made its debut in 2005, the presence of ‘550’ on the backside of a petrol 5 Series has always meant one thing: a thumping V8 up front. This, of course, changes for the latest generation, but the loss of two cylinders hardly portends a shortfall in performance.

A recorded 0-60mph of 4.4sec makes the 550e 0.2sec quicker than the V10-hearted E60-gen M5, and we suspect this is also the first sub-M-car to sprint to 100mph in less than 10sec.

One reason the 550e is so savage when it comes to roll-on acceleration in second and third gear could be to do with BMW’s patented pretransmission ratio, which multiplies torque from 184lb ft to an effective 332lb ft, negating the need for a bigger motor. It really pins you back.

Of course, the hottest PHEV 5 Series barely hints at this sort of pace when you first slide aboard. Defaulting into EV mode, it pulls off the mark with barely a ripple, the straight six igniting only once battery charge is depleted, when a serious bout of acceleration is called for, or when you put the gearbox into ‘S’ mode, for snappier upshifts programmed to slot home closer to the 7400rpm redline.

The nature of the performance is familiar – as a non-M model with a torque converter, gearchanges aren’t whip-crack fast, but this ZF unit (now with an upgraded oil pump and improved vibration damping) continues to ensure there’s no meaningful break in the considerable flow of torque.

The linear B58 motor is as sweet as ever, too. It develops peak torque at 1750rpm, sustaining it until nearly 5000rpm. Does this motor justify the £17k premium the 550e asks over the four-cylinder (and purely RWD) 530e? Rationally, no, but any 550-badged 5 Series has always been more about ‘want’ than ‘need’.

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As for the lack of a V8, it is a shame, but the 550e has one trick up its sleeve beyond its ability to unobtrusively slip between electric and combustion propulsion (and, if you so choose, return long-term economy stats of which owners of the old 550i could only have dreamed). In Sport mode, hybrid assistance means tip-in throttle response is outrageous. The 1.9sec taken for the 20-40mph dash in third gear actually beats that of the M5 CS we tested in 2021.

However, gut-punch speed is a quirk of the 550e, not a hallmark. It’s mostly a relaxed, tourer-type personality, capable of wild pace at the drop of a hat but never much encouraging you to overindulge in it, as an M5 does. Happily, the 550e’s Q-car credentials remain intact.

While the 550e is the star of the 5 Series line-up (until the M5 arrives, at least), most buyers are likely to choose the 520i or 530e. Thankfully, those versions impress as well. The 530e plug-in hybrid lacks the kudos of the 550e's six-cylinder, it certainly doen't lack for everyday performance. With the same 181bhp electric motor, it can do a creditable impression of an EV in electric mode, and manages its power very cleverly to subtly augment the 2.0-litre petrol engine to make it feel more muscular and effortless than it otherwise would be. Even when the battery is depleted, the software keeps a decent amount in reserve in order to function as a full hybrid.