Wider rear wheelarches and a thin red light strip across the rump: that's all that distinguishes the new Porsche 911 Carrera 4S from its Carrera 2 stablemates. Time to find out if all-wheel drive makes the impressive 991 even better.

What's different under the skin of the Porsche 911 Carrera 4S?

The latest example of the four-wheel drive 911, this wide body, wide track 991 C4S commands a £7000 premium over its two-wheel drive sister models. Porsche still uses two packs of wet multi-disc clutches to relay torque between the axles and the rear wheels – a compact and light set-up – and in normal operating conditions, the C4S drives only the rear wheels, so the 50kg weight penalty has little effect on fuel consumption.

Does Porsche's all-wheel drive make a difference in wintry conditions?

Throw in a slippery surface, and the torque split will vary according to the calculations of Porsche’s Traction Management system (PTM). In an extreme situation, with the rear wheels on black ice and the fronts on dry Tarmac, the 911 will momentarily turn into a 100% front-drive car. You can provoke a torque shift to the front wheels by accelerating hard on slippery ground with ESP switched off – but as soon as the car turns in, PTM will adjust the torque flow so that it does not over-tax the lateral grip of the tyres. Clever, that.

Can you really feel the difference between the C4S and a regular Carrera 2 S 911?

It takes a winding uphill road with added rain, snow or gravel to really feel the advantage of the Carrera 4 over the 2, the former dispatching the oomph to the necessary wheels in a fluent, progressive way. You’d be thankful for it on the final 200 yards to the ski lift or on the bumpy trail to the beach. The optional PDK transmission is very quick, but the standard manual seven-speeder is a haptic delight, the ratios perfectly spaced for optimum grunt and economy.

Verdict

A C4S drop-top with PDK would make a compelling four-seasons all-rounder and a near-supercar for half the price of a Bentley Continental GTC W12.