Engine options, top speed, acceleration and refinement

As with any luxury limousine, having a surfeit of power and performance is desirable not because you will ever need or want to use it, but because it allows the car to propel itself in truly insouciant fashion during day-to-day driving.

The S580e, with its 503bhp PHEV powertrain, acquits itself well in this respect. Without any launch control function (why would there be?), the car sprinted to 60mph in 5.2sec at Millbrook, but this is by the by. The car’s ability to shoot from 30mph to 70mph in 4.2sec is a more relevant indicator of muscular real-world performance, and the 6.3sec required to cover that increment in fourth gear comfortably beats that which we recorded for the Audi S3 – an immensely swift hot hatch.

It remains tidy during brisk driving, aided by strong grip, excellent traction, pleasing steering response and measured body control, but it’s less sporting than the 7 Series.

The nature of that performance is what really matters, though. Aided by substantial torque from the electric motor, the S580e’s turbo straight six likes to live its life in subdued fashion, and the nine-speed gearbox will covertly shuffle cogs to ensure crankshaft speeds rise above 1600rpm or so only when necessary.

That’s if the engine is even running. Whereas comparable PHEV versions of the Audi A8 and BMW 7 Series merely pay lip service to the idea of all-electric running, the battery pack in the S580e is large enough to yield 62 miles on paper and around 45 miles in the real world. You can either select a dedicated EV mode and use battery power exclusively, or allow the car to juggle ICE and electric power in Hybrid mode, which it does deftly and effectively.

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We were surprised at just how little the engine is used beyond instances where reasonably swift acceleration is required, or sustained cruising. The car also makes good use of its regenerative braking function, which is aligned with the navigation data and exterior sensors to adapt to road furniture and other cars up ahead. So slick is the calibration that it doesn’t take long to fully trust in and work with it.

Another area of strength is the calibration of the motor and engine responses. The car accelerates crisply thanks to the electric portion of the driveline and is joined seamlessly with combustion power when necessary. Never is the power delivery lumpy or uncomfortably reactive, and this applies as much to roll-on acceleration as it does to low-speed manoeuvring. Less impressive is the gearbox’s tendency to occasionally hiccup during the multiple downshifts required when coming to a complete stop. For an otherwise seamless – if relatively uncharismatic – affair, these jarring little interjections are unwelcome.