The question of whether to choose petrol or diesel when buying a car is certainly not a new one, and it's also one to which there is no straightforward answer. Many people will find they have an automatic preference based on their past motoring experience.
Diesel engines have long shed their reputation for being reliable but slow, and thanks to advances in technology they have become ever more popular with UK consumers. Sales of diesel-powered vehicles overtook sales of cars with petrol engines for the first time back in 2010 and this trend has continued. According to the Society of Motor Manufacturers and Traders, 1,240,287 diesel cars were registered in Britain in 2014, compared to 1,184,409 petrol vehicles.
So what about the new Ford Focus ST?
Petrol - Ford's updated petrol powertrain is the 250PS 2.0-litre EcoBoost. Thanks to turbocharging, twin-independent variable cam timing technology and high-pressure direct-injection, it's capable of taking the five-door and estate STs from 0-62 mph in 6.5 seconds and 6.7 seconds respectively, before pushing through to a top speed of 154mph.
The EcoBoost achieves peak power at 5,500 rpm, while 360Nm of torque is available from 2,000-4,500rpm. In terms of fuel efficiency and environmental impact, both bodystyles can achieve 39.2mpg combined, while CO2 emissions are kept to 169g/km. With the EcoBoost powertrain there is also the option of having Auto-Start-Stop technology fitted, which will improve fuel efficiency by 6 per cent and reduce CO2 emissions to 159g/km.
Diesel - Opt for the new diesel kid on the block and you'll get a 185PS 2.0-litre Duratorq TDCi engine complete with Auto-Start-Stop technology as standard. Electronic calibration, an updated air intake system along with a new sports-tuned exhaust all help to deliver hot hatch-standard performance.
The five-door and estate models will go from a standing start to 62mph in 8.1 seconds and 8.3 seconds respectively. Peak power is developed at 3,500rpm and there's 400Nm of torque available from 2,000-2,750rpm, which will push the car to a top speed of 135mph. Both the five-door and estate versions offer fuel consumption rates of 67.3mpg and keep CO2 emissions to 110g/km.
Regardless of whether you're looking for the raw performance of a petrol engine or the everyday practicality and greater fuel efficiency of a diesel, there's plenty of fun to be had behind the wheel of the new Ford Focus ST. The engineering work that has gone into updating the ST's steering, suspension and electronic control systems means greater precision, responsiveness, agility and a more exhilarating driving experience right across the board.
What's more, if you're prepared to see a little performance shaved off, the estate or wagon model of the new Ford Focus ST offers a highly practical solution for drivers who require plenty of flexible loadspace to play with. It's ideal too if you need to regularly transport the family but don't want to miss out on the fun that comes from owning a true performance car.
If your focus is purely on performance then the five-door petrol EcoBoost version with its incredibly snappy 0-62mph time of 6.5 seconds is the obvious choice. Choose to have Auto-Start-Stop technology installed and you'll also be behind the wheel of the most fuel-efficient petrol Focus ST ever.
Of course the standout figure from the Duratorq TDCi powerplant is its ability to achieve 67.3mpg while still putting in a solid performance off the line. If you're looking for a hot hatch that takes day-to-day usability and sports styling to a new level, then give serious consideration to the most fuel‑efficient and lowest CO2 performance car that Ford has ever produced.