Even with just a 2.0-litre four-cylinder engine, with petrol prices being what they are, it was a sizeable disincentive. It would only do 25mpg if you drove it unusually gently.
So what hope, then, for the S-Class, with its similar weight and a 3.0-litre six-cylinder engine?
Of course, the secret lies in its ability to travel a considerable distance on battery power alone (of which much more in a minute), but it’s easy to exclude that from the reckoning just by pressing the ‘battery hold’ icon on the touchscreen. And what’s astonishing is that, even if I factor in the usual optimism of the Mercedes trip computer (why are they allowed to not tell the truth?), it will still do close to 40mpg without depleting its electrical reserves in the slightest.
For that, I can thank a shape that is to the Defender as a pencil is to a house brick, but also an astonishing ability to scavenge energy in the most unlikely of circumstances. Find myself on the gentlest downhill gradient and it will have the engine off in an instant, stopping dead all those energy-sapping reciprocating masses, because it has figured out that it can maintain progress on the energy it’s recovering without troubling that in the battery. Sometimes I even see the electric range increase by a mile or two.
But actually I spend as much time as possible driving it on electricity sourced from my wallbox at home. Because it has a chunky 28.6kWh battery, that gives it a claimed range of 63 electric-only miles. Compare that with the 25 miles of the Bentley Bentayga Hybrid that I ran on this fleet earlier in the year.
Actually, and now that it has learned a bit about me, how and where I tend to drive, the Benz is estimating (and delivering) around 66 electric-only miles.
So unless I’m going a long way, this ultra-luxury, long-wheelbase limousine, with its 2.4-tonne kerb weight and more than 500bhp, has the lowest energy cost of any car that I’ve ever owned or run.
Even long journeys, like my typical trundle to London and back, will yield well over 50mpg without me recharging it in the city.