An AMG edition of the GLC medium sports utility is expected to further enhance the popularity of a model already going gangbusters here.

NOT only will the performance AMG version of its GLC further liven interest in a strong-selling Mercedes New Zealand star, it might also cement an already strong customer preference that has surprised the distributor.

At present Benz here offers the GLC in three formats, a 2.1-litre diesel in two states of tune, and a 2.0-litre petrol.

The arrival, toward the end of the year of a racy flagship bringing a twin-turbocharged V6-powered GLC43 seems to even the fuel preference score.

However, general manager Ben Giffin says customers have already determined the petrol $94,900 GLC 250 here already is the one they like best; once the GLC43 comes along late year, the swing toward that side of the forecourt will become all the more pronounced.

While the local boss is unable to provide exact data, he says the GLC250 choice is comfortably outselling the $89,900 GLC 220d and $96,900 GLC 250d.

This brings an element of surprise – within the overall medium SUV sector, diesel has in the past been such a dominant choice Benz appeared to be particularly adventurous in deliverying even one petrol.

“We’re the only luxury manufacturer with a petrol mid-sized SUV … it’s hard to say what percentage of total sale is taking but we ordered the cars in very specific counts in reflection of our expectations … and the petrol is doing better than we imagined.”

Yet there are no plans to consider whether Benz has one diesel too many, because all three variants are achieving enough interest to earn their keep. Also, there’s not yet a situation where an order bank has begun.

The engine types seem to have different priority in different areas; the petrol has established most strongly in Auckland, whereas the diesels are still holding greater sway in the South Island.

“Our customers there, and in other rural locations including the Waikato, still enjoy diesel.”

GLC has got off to a strong start, though; in the four months it has been on sale, this new model has wasted no time in establishing as the top-selling Benz sports utility. Again, that was unexpected: There was every thing the updated large GLE (previously the M) would maintain that mantle.

“GLC has really exceeded our expectations. It’s something that was missing from our model range for many years … we knew that not having it was a chink in our lineup.

“It has become a huge success; already we think that it will end the year as our leading SUV in our lineup.

“GLE is still extremely strong for us and there is always the customer base that prefers a larger SUV, but there’s no doubt that the market, particularly in New Zealand, is going towards that medium-sized SUV.”

GLC’s status will assuredly grow with the 43. The first mid-sized SUV from the German-car maker to receive special treatment at the Affalterbach factory, it generates 270kW and 520Nm from its 3.0-litre V6 – some 115kW and 170Nm more than the GLC250 creates.

Benz says this model accelerates from standstill to 100kmh in a swift 4.9 seconds, but despite the feisty performance, it manages an optimal fuel efficiency of 8.1 litres per 100km on the combined cycle.

Ultimately it will play second fiddle to an even hotter AMG-ised GLC. Though the full-fat V8 GLC63 version is officially still awaiting confirmation, there’s every chance it will come – but perhaps not until the 43 has had at least a year in the market.

Giffin is excited by the prospects the 43 delivers. “The AMG is such a strong brand in New Zealand. It’s performance here has been exceptional. The 43 is just going to be another one of those cars that offers great potential for us.”

He doubts it will diminish interest in the other GLC models but instead will conquest; he imagines current owners of the Audi SQ5 might be swayed to shift brand allegiance, even though the Ingolstadt project is a diesel. Likewise some owners of high-end BMW X3s that, again, are oilers.

The new flagship makes its official public debut at the New York motor show next week.

The six-cylinder is largely similar to other high-output V6s in the company's repertoire, but for the GLC, Mercedes has altered boost pressure and tailored engine management mapping.

Power transfers via the 4Matic transmission and the widely used nine-speed 9G-Tronic automatic transmission, which has five Dynamic Select driving modes – Eco, Comfort and Manual for more day-to-day driving or Sport and Sport Plus to make the most of the urge.

When in the performance settings, Mercedes says a “double declutching” function produces the fastest and most involving gear shifts. Steering wheel paddles can be used to change gears manually for the control freak. Also, torque is split between front and rear axles 31:69 respectively, when the power modes are enacted.

The GLC43 has Comfort, Sport and Sport Plus settings for the Air Body Control pneumatic suspension. The four-link suspension set-up at the front has more negative camber for greater cornering grip, while the ride is stiffened over the standard GLCs.

Steering and accelerator sensitivity are also adjusted in the various diving modes, with a faster rack-ratio and greater weight in sportier modes, while a higher idle speed allows a quicker getaway from standstill.

The AMG stands apart by having more chrome and gloss black highlights, different front and rear bumpers and a scattering of AMG badging. It also has bespoke 19 inch rims – though 21s are optional - and has quad exhausts.

On the inside, the Mercedes-AMG treatment continues with a D-shaped black leather steering wheel with contrasting red stitching and multi-function controls, sports seats keep front passengers pinned in a combination of synthetic leather and suede with more red thread.

A 5.5-inch AMG-specific instrument cluster provides the driver with vehicle information and is decorated with a “chequered flag look” for more sporty appeal. Sports seats and carbon fibre inlays are optional.