Petrol power, diesel economy from Merc - How does it work?

Here's the technical bit... The 1.8-litre Diesotto engine is a four-cylinder, twin-turbo unit that runs on standard petrol. Like any petrol engine, the Diesotto engine has spark plugs at the top of each cylinder, but they don't fire on every cycle.

They will fire if the driver accelerates hard, but otherwise the engine will rely on the natural heat generated by compression to ignite the fuel mixture, just like a diesel engine.

There is also a battery-powered electric motor to complement the petrol engine, and the result is that the F700 is able to run economically in mundane motoring situations, but there's available power if a driver wants to accelerate hard.

So how did it feel? Our impression, albeit as a passenger, was that the power system (Diesotto/electric hybrid) worked really well. Power delivery seemed smooth, acceleration seemed quick and didn't feel in any way unrefined.

Why the odd name? Well, the engine takes its name from Rudolf Diesel, inventor of the diesel engine, and Nikolaus Otto, inventor of the petrol engine.