WE are about to witness a very important public experiment.

Will Mercedes-Benz customers pay top-dollar for a performance diesel in a C-class?

The company admits it is taking a risk, but believes choosing the diesel C320 instead of the C350 petrol model was the right decision.

We haven't driven the new C350, so it’s not possible to cast an opinion on the decision itself, but we can weigh up the pros and cons of the C320 CDI.

This is a very strong engine.

Just consider the fact that its muscular torque total of 510Nm matches the output of the about-to-be-replaced C55 AMG V8.

The C55 delivered that amount of torque at 4000rpm, while the C320 diesel punches it out from just 1600rpm.

Of course, the comparisons end there because the C55 can rev much higher and delivers 105kW more power.

Even so, the torrent of torque the C320 can unleash makes it an impressive drive.

It hustles along a mountain run like a true performance car, with its turbo-boosted engine offering all the pulling power you need – and more.

It is especially good for slinging out of corners. The surge from 60km/h to 100km/h is simply stunning.

The seven-speed automatic transmission is well matched to the engine and the shifts are fast and smooth.

You can choose to change gears yourself using the shifter, or via the paddles on the back of the steering wheel if you choose the optional AMG sport pack.

We found the transmission works so well and there is such a tremendous reserve of torque that you don’t need to over-ride the automatic gearbox.

Just leave it in drive and let the turbo do all the work.

However, while the diesel engine has its own charms when pushing hard, it is a different sensation to pushing a naturally-aspirated petrol engine.

For example, the super-smooth in-line six-cylinder petrol engine that powers the BMW 325i sings beautifully close to the redline. It is great fun to play around at the top of the rev range as you push along twisting roads enjoying the wonderful exhaust and induction note.

The C320 is a different beast.

The enjoyment comes in the form of the wave of torque that kicks-in low down in the rev range. There is no need to wring its neck and rev it out because the powerband is down the bottom.

It certainly doesn’t sound like a diesel engine when you are pushing hard, as there is no rattle or high-pitched clatter.

There is a slight hint of a sporty exhaust note, but it doesn’t sound anywhere near as aggressive as a performance petrol engine would.

At lower speeds, the engine does sound like a diesel. It’s is a very quiet and very refined engine, but you can still pick the diesel sound.

Some people won’t mind at all given the tremendous urge the engine offers, but we are tipping that some luxury sedan customers might find it a bit hard to get used to.

Customers are likely to enjoy the fact they won’t have to visit the petrol pump as much as they would if they had a V6 petrol engine under the bonnet.

The problem remains that the lack of appropriate diesel pumps and the condition of many of the existing ones is likely to put some people off.

Despite some new diesel pumps being installed, there are still some service stations that don’t have diesel and even more that only have high-flow nozzles that don’t fit passenger cars.

Some are also quite messy, something that passenger car customers might not be used to. The C320 is a convincing package, as are the other models in the new C-class sedan range.

Mercedes engineers have done a good job of balancing good ride quality and sporty handling.

The C320 is comfortable and rides very nicely, yet it manages to sit fairly flat through the corners.

It is not quite as agile as a 3 Series BMW, but is more comfy to ride in.

The steering is well weighted and there is good feedback.

Mercedes has also done a quite good job with interior noise supression and there is very little tyre or wind noise in the cabin.

There is good head and legroom for front and rear passengers.

Mercedes has done a pretty good job with the interior, although the cabin of the C320 doesn’t look all that much more special than the considerably cheaper entry-level model.

The instrument panel looks similar to that of the S-class, but the rest of the dashboard looks a little plain.

The Command APS sat-nav/music display sits in the dashboard behind a cover and then pops up when you need it. To be honest, it looks like a bit of an afterthought.

The C320 is not cheap at $92,800, but the engine represents a significant improvement over the 170kW 3.0-litre V6 petrol engine in the C280.

Some luxury sedan customers might not be ready for a diesel powerplant, especially in the headline model, but the tremendous torque of the C320 does make a convincing case.