Kiss 92FM was playing American singer Mary Lambert's hit song Secrets on the radio when I drove the Mercedes-AMG C63 S test car out of the basement carpark of Daimler South East Asia's office at the Centennial Tower last week.

I didn't know it at the time, but that song would turn out to be a reasonably accurate prediction on how the C63 S would turn out to be.

For those unfamiliar with the song, the opening lines go like this: "I've got bipolar disorder/My s**t's not in order/I'm overweight, I'm always late/I've got too many things to say."

The C63 S certainly isn't overweight and those driving AMG fast cars are unlikely to be late for appointments, but its behaviour is symptomatic of someone with bipolar disorder.

It is a practical family saloon which can accommodate three adults at the back with reasonable comfort, but a mere flick of a "drive mode" switch and a slight tap on the throttle turn the car into a Porsche 911 Carrera S-beating sprinter.

The engineers at Mercedes-AMG have slotted its latest 4-litre, twin-turbocharged V8 engine, also found in the AMG GT S, into the body of a C-Class saloon.

The operation gives the car a split personality - it is upmarket enough to be parked next to luxury cars at the driveway of the Fullerton Hotel and fast enough to keep pace with Porsches and Ferraris on the race track. Mercedes-Benz's official press release on the C63 S AMG describes it as a "powerful high-end sports car". The German carmaker was unnecessarily modest.

The C63 S is the most powerful model in the C-Class line-up. The press car came with an Edition 1 tag, which is what Mercedes-Benz calls its AMG cars in their first year of production.

The Edition 1 features include red accents on the radiator grille, the wheels and the door mirrors; a subtle gloss black spoiler and four chrome tailpipes at the rear. These visual enhancements cost an extra $27,900. Inside the cabin, the car has frills commonly found in luxury cars, such as a panoramic sunroof and Burmester surround-sound system.

The high-end sound system is unnecessary because the best sounds of the car come from the engine, not the speakers.

When fired up, the V8 engine produces a confident and bassy purr. And the purr turns into a roar at the slightest pressure of the throttle pedal.

In AMG tradition, the engine parts are assembled and fitted by hand by an AMG-certified engineer who signs his name on the engine block cover. The engine is paired with Mercedes-Benz's capable seven-speed automatic gearbox that comes with paddle shifters.

The C63 S rockets from standstill to 100kmh in four seconds, which puts it in the borderline supercar speed territory.

Its V8 engine is not just about horsepower and torque. With a fuel consumption of 8.4 litres per 100km, it is also relatively frugal for an engine of its size.

My 140km test drive over one day turned in an average fuel consumption of between 11 and 12 litres per 100km, but that was because the six-week-old test car, with barely 1,300km on the clock, was not fully broken in yet.

The car's carbon emission of 192g/km puts it in the C1 band which draws a penalty of just $5,000 - this is a feat considering that bigger capacity engines are more polluting. In fact, the test car registered on June 29, just two days before the new Carbon Emissions-Based Vehicle Scheme kicked in on July 1, drew neither penalty nor rebate because it was considered to be pollution- neutral.

On the go, the C63 S offers four basic pre-configured drive modes: Comfort, Sports, Sports+ and Race. The suspension stiffens and gearshifts quicken progressively from the Comfort mode. I tried all drive modes except the Race mode because the only place to test the Race mode safely with its limited traction control and launch control feature is the race track.

Still, these various drive modes pack some surprises.

When left in Comfort, the car is a comfortable daily cruiser not unlike a regular C-Class or even the E-Class. Its sporty exhaust note can even be switched off to cloak its race car DNA (but why would anyone do that?).

The car also allows drivers to customise the settings for the engine, suspension, transmission and exhaust sound. My favourite combination is the Sports+ mode - in which the car is at its friskiest and the exhaust sound is loudest - and the Eco mode, which shuts off the engine at traffic lights.

It is bipolar behaviour, a contradiction of sporty driving while trying to go green at the same time.

At a traffic light in Ang Mo Kio, the driver in a WRX stopped next to me, wound down the window and had a puzzled look on his face. He must have wondered why my car did not sound like it has an AMG engine because it was as quiet as a sleeping kitten.

His puzzlement must have turned into shock when the lights turned green, the silent engine fired up and I jack-rabbited off. He did not try to give chase.

While the sound of the AMG engine and its exhaust note were exhilarating, the test car had another less welcome sound.

It rained for most of the afternoon during my test drive and the wiper blades juddered so badly that it destroyed the aural pleasures of driving an AMG car.

As the wiper blades swept across the windscreen, I could hear a steady 10-beat "Da-da-da-da-da, da-da-da-da-da" rhythm. I hope that the flaw was a temporary one because the wiper blades were still new.

Nevertheless, the C63 S offers drivers an attractive combination of good looks, poise and speed. Excluding the 2-litre AMGs such as the A, CLA and GLA, the C63 S and its C63 twin with a lower engine power output are the entry-level big-engined AMGs.

The bonus of a sub-$500,000 price tag makes the entry to the hallowed AMG club affordable, relatively speaking.