How does the new hybrid tech in the Peugeot 3008 and 5008 work?

Hybrid? I thought hybrid Peugeots had a plug?

Indeed, Peugeot has been making PHEVs for years, but this is a new milder non-plug hybrid that's supposed to do the job of a diesel: give you torquey performance with a useful economy boost versus a pure-petrol. Only it's quieter than a diesel and waaaay more fashionable.

OK, what's the tech overview?

The transmission is a new six-speed twin-clutch auto, with a 48-volt motor built directly in. The motor can provide up to 28bhp, so it'll start and drive the car at low speed or light accelerator pressure without help from the engine.

For that to happen, there's a third automatic clutch that separates the engine from the motor-transmission unit and allows the pistons to sit silently still, using no fuel, when not needed. When you do need the extra heft of burning petrol, another electric machine wakens the engine rapidly. This is a belt-driven 48V starter-alternator, replacing the usual 12-volt items.

The 48V battery, just 0.43kWh, sits under the left-hand front seat. The rest of the car runs on 12V as usual, thanks to a voltage converter off the 48V system.

Peugeot's familiar 1.2-litre engine got quite a going-over. Most conspicuously, it now runs the Miller cycle, which delays the closing of the intake valves, over-expanding the combusted mixture for better light-load efficiency.

Does it work?

In the official tests, yes. The WLTP fuel saving versus the normal petrol is about 15 per cent, and the CO2 number is cut by 20g/km.

Sure enough in town the engine goes to sleep often. The car can trickle along on electrons alone for maybe half a mile. We found this even when testing on a mad-hot day in Spain with the air-con on.

The fuel savings come because the system runs the engine closer to its most efficient revs or otherwise stops it. It also uses some of engine power to charge the battery, when not needed for the wheels. More savings come from regenerative braking via the electric motor. This is all standard-procedure hybrid stuff.

But similarly no hybrid does much to help steady-state motorway cruising. The savings come at lower and variable speeds.

How does it feel?

The peaceful electric running is always nice to have. Also, unless you're paying special attention, the starting and stopping of the engine is wholly fuss-free.

If you've got the stereo on, the only sign is blue speedo numbers when the engine's off and white when it's on. Oh, OK, you can also call up various hybrid energy displays in the screens.

With the torque-fill from the e-motor, turbo lag is masked and six gears are enough. It generally feels more lively than the naked 1.2 engine. Gearshifts are smooth, and if you don't like its decisions it has a proper over-ride via an M-for-manual switch and paddles behind the steering wheel.

Braking from 40mph or so can feel a little strange, as the motor tries to regenerate as much energy as it can. But that's a fair price to help you go further on your petrol.

Unlike Peugeot's PHEVs the whole system feels more natural when you're working the throttle on twisty roads.

What's the future?

Before long we'll see the system in the 208, 2008, 308, 308 SW and 408.

But it's launching first on the 3008 and 5008 crossovers. TopGear.com suggested this is an odd decision as the 3008 has just a year left to run before an all-new one arrives, on an electric platform. The Peugeot strategists point out the 3008 is a massive seller and worth supporting even in its dotage.

An odd coda is that it was under development before the merger of PSA with FCA to form Stellantis. So we find Alfa has a similar concept but differently executed on the Tonale. That one has a seven-speed DCT and Alfa's own 1.5-litre four-cylinder engine.