What is it?
 
An all-new Mercedes SLK55 AMG, the entry point into high-performance Merc ownership. Like the bulk of the AMG range a 5.5-litre V8 engine sits in the front; however here, it’s naturally aspirated.
 
Technical highlights?
 
Effectively a naturally aspirated version of the 5.5-litre Bi-Turbo V8 in the E63 et al, the engine produces 416bhp and 398lb ft, ample in something so compact and weighing 1610kg.

The clever news is the cylinder de-activation system that allows the car to drop four cylinders at a pootle, between 800rpm and 3000rpm. This brings huge gains in efficiency and, combined with stop/start promises 30mpg at a cruise.
 
The car itself sits lower and squatter than a standard SLK, Springs and dampers are firmer and it places more rubber on the road. Our test car was fitted with the optional Handling Pack, which adds a limited-slip differential and firmer springs and dampers.
 
What’s it like to drive?
 
Performance is strong, throttle response is very sharp and it loves to rev out with a big V8 shout. This is the first AMG to use electronic valves in the exhaust boxes, and they’ve been subtly integrated. The electric power steering is accurate, if a little numb and seems to offer unnatural resistance if you want to make an adjustment mid-corner. The SLK isn’t a great communicator.

What it is, is a kind of mini-hot-rod. Plop it in D, drop the roof, antagonise the odd M3, and then remark to yourself, and your co-driver, that the SLK 55 is actually far better at the business of going fast than its slightly girly image would suggest. It’s frugal too: mooching between 55 and 75mph I managed 34.9mpg, which is mighty impressive. The optional firm suspension is too harsh for such a cruiser.
 
It’s actually quite the yobbo, if you feel inclined, but then do people want that type of character in an SLK bodyshell? Who can tell. It remains an interesting curiosity with some unexpected running-cost advantages, but I can’t help wondering what this powertrain would be like in a C-Class.

How does it compare?
 
There’s no BMW Z4 M (yet) and the most powerful Porsche Boxster has just 316bhp, so the SLK AMG is more a rival to a folding hard-top equipped M3 than anything else. The BMW boasts similar power (414bhp) but is lacking in torque (295lb ft) and mpg (22.2). With four seats it’s less of a compromise, though, and better to drive than the SLK.
 
Anything else I need to know?
 
This is the most fuel efficient V8 car in the world, and emitting just 195g/km of CO2, it falls into the same UK tax band as a 2.0-litre, four-cylinder Renault Clio Cup.