The Mercedes A 45 AMG is a car of extremes. It's the smallest AMG-badged car currently in production, and Mercedes claims (and we have no reason to doubt) that it has the most powerful four-cylinder engine in the world. With over 350bhp it's also one of the most powerful hot hatches currently on sale.

Its main challenger is the more recently introduced Audi RS 3 Sportback. This is even more powerful, but that situation will change when the revised A 45 comes along. That car is available to order now, but UK customers won't get their hands on it until September 2015. The original model is still available while stocks last, and is the one being considered here.

Performance

With 355bhp from its 2.0-litre turbo petrol engine, along with four-wheel drive and the very effective Race Start launch control system, the A 45 fairly rockets away from a standing start. It can go from zero to 62mph in just 4.6 seconds.

The top speed is limited to 155mph, though you can have this raised to 168mph if you pick the £1,940 Driver's Package, which also includes attendance at an AMG Power and Passion driving event.

Despite the engine's small size relative to its power output, it's very flexible, being capable of producing over 140bhp at just 2,250rpm.

The revised car will be faster still. It will have a maximum of 376bhp, and the upper gears in the 4MATIC seven-speed automatic gearbox will be lower than they are at present. Mercedes is quoting a 0-62mph time of 4.2 seconds, and in-gear acceleration will certainly be improved.

Ride and Handling

The ride quality is quite good, but there is very little feel through the steering, and it can take a long time to believe that the car will go through a corner as quickly as it actually can.

Even on the standard suspension's Sport setting the A 45 feels far less like a race car than its straight-line performance would suggest. The ride quality is quite good, but there is very little feel through the steering, and it can take a long time to believe that the car will go through a corner as quickly as it actually can. Firmer suspension is available as an option. Mercedes has revised the settings for the 2015 car, and assuming the job has been done well it will no doubt feel a lot better than the current one does.

Interior and Equipment

Every AMG engine is put together by one of around 50 Master Engine Builders, whose signature can be found on an engraved plaque.

The dark but attractive interior design will be quite recognisable to anyone familiar with other Mercedes models. The only real problem with sitting inside the A 45, and indeed any other A-Class, is that it's difficult to see out. Reversing, in particular, would be a lot easier if the rear windows were larger. Practicality may not be the first reason for buying a car like this, but for the record the A 45 can carry 341 litres' worth of luggage with all the seats up. Load capacity increases to 1,157 when the rear ones are folded down. For a car costing nearly £40,000, the level of equipment is less than lavish. DAB digital radio is fitted as standard, but you have to pay £495 extra for satellite navigation. Other items available only at additional cost include rear side airbags, tyre pressure monitoring and the COMAND online system (£2,100 if it includes a single CD player, £2,300 with a 6-disc changer). Other optional kit includes heated front seats and a £1,530 Aerodynamic Package which is probably more cosmetic than effective.

Cost

While this is far away from being the cheapest hot hatch in terms of either purchase or running costs, it is cheaper to run than the Audi RS 3 Sportback.

The list price is just over £38,000 (the upcoming revised model will start closer to £40,000) though with options you could easily take it over £50,000. Combined fuel economy and CO2 emissions are 40.9mpg and 161g/km for this car and will be almost exactly the same for the new, faster one. Vehicle Excise Duty will cost £180 from year two onwards under the current system, while Benefit In Kind taxation is currently 27 per cent and will rise steadily to 36 per cent for the 2019-20 financial year. While this is far away from being the cheapest hot hatch in terms of either purchase or running costs, it is cheaper to run than the Audi RS 3 Sportback.

Our Verdict

The A 45's party trick is the way it sizzles away from a standing start. Through corners it's effective but not particularly exciting, though in the near future we’ll see if Mercedes has managed to improve its handling while developing the uprated model. Running costs are fairly competitive, relatively speaking, but we'd like to have seen more equipment being included as standard for the price. There are also other hot hatches around which, while far less powerful, offer more fun for a much lower price.