The UK's premier eco-driving event has proven that even a performance car can be parsimonious, with a 5.0-litre V8 Ford Mustang taking the most coveted prize in this year's event.

The Mustang achieved 36.6mpg overall against a manufacturer's combined figure of 20.9mpg over the 387-mile route on the MPG Marathon – a 75.12% improvement and the highest percentage improvement figure ever on the event.

Meanwhile, the best overall fuel economy for a combustion-engined production car went to a Mazda 2 1.6d Sport Nav which achieved 91.37mpg, an improvement of 8.27mpg or 9.95% over the manufacturer's combined figure, though the crew did incur a 2.5mpg time penalty reducing the improvement to 5.77mpg or 6.94% in the final tables.

The highest overall figure was achieved by a pre-production Toyota Prius Plug-in Hybrid, with 109.14mpg achieved. At the UK's average fuel cost of £5.20 a gallon, this equates to just £14.63 worth of fuel to drive a route equivalent to the distance between London and Glasgow by road.

In an event described by a number of competitors as the toughest MPG Marathon yet and sponsored by RAC Business, ALD Automotive and Crystal Ball, drivers were charged with working out the most economical route between a number of waypoints in Oxfordshire, Warwickshire, Shropshire, Northamptonshire and Gloucestershire in a two-day event starting and ending near Chipping Norton in the Cotswolds.

Event organiser Jerry Ramsdale said: 'The diversity of vehicles in the event this year was tremendous, and showed just what can be achieved by adopting a level of eco-awareness from behind the wheel.

'The achievement of the crew in the Ford Mustang was astonishing – our highest improvement ever in the history of the event – and it shows that even the most potent performance cars can be relatively economical if driven sensibly.'

In the light commercial vehicle category a Fiat Professional Fiorino 1.3 MultiJet achieved 72.08mpg, a 12.28% improvement over its quoted MPG figure of 64.2 mpg.

Mr Ramsdale added: 'Improvements in fuel economy, not to mention carbon footprint, are very important for fleet managers who run vans, as they tend to operate large fleets where even the smallest of savings can have quite a significant impact on a company's bottom line.

'The MPG Marathon proves how even small improvements can make a big difference, and how important it is for fleet managers to educate their drivers in the art of driving economically.'

After covering a total of 8,277 miles in two days, the entrants in this year's MPG Marathon improved their vehicles' fuel consumption by an average 9.98mpg – a figure that could save fleet maanagers up to £400 a year per driver.

Based on an average of 46.94mpg as the manufacturers' combined MPG figure for all the production cars and vans taking part in the MPG marathon entrants achieved a mean average fuel consumption figure of 56.92mpg, an improvement of almost 10mpg, or around 21%.

With fuel currently costing an average of £5.20 a gallon in the UK, and likely to increase due to falls in the value of sterling, the competitor cars saved an average of £8.46 a vehicle over the route of nearly 400 miles. Put into context, this could save fleet managers operating fleets where drivers cover 400 miles a week around £400 per driver, per year – a significant saving.

Other notable entrants included a hydrogen fuel cell-powered Hyundai ix35 which used 6.45kg of hydrogen during the event, averaging out at 63.1 miles per kilo against a quoted figure of 60.9 miles per kilo.

Driver by Chris Chandler, principal Consultant at Lex Autolease, said: 'This is a great result for the Hyundai ix35 Fuel Cell and truly demonstrates the capability of advanced fuel technologies.

'There was significant interest in how the ix35 performed both at the event and across social media, with people hungry to find out more about how hydrogen-fuelled vehicles work and what the potential benefits are. It's clear the technology will play a central role in the industry's future. The car is a working vehicle, used on a daily basis by the University of Birmingham and our fuel-efficiency results speak to its potential – the only emission produced throughout the race was water.'

New for this year was a Garage 56 category, open to experimental and unusual vehicles and named after the prototype garage at the Le Mans 24-hour race. As well as the Prius and ix35, other Garage 56 vehicles included a Moto Guzzi 750 motorcycle, a Mercedes-Benz E220d driven in semi-autonomous mode and an Australian-made V8-engined Vauxhall VXR Maloo 'Ute' pick-up.

For the first time, fans of the event were able to track the vehicles' progress live using telematics data supplied by sponsor Crystal Ball, which broadcast where each car or van was at any given time via the event website.

To view the breakdown of all the winners and find out more about the event log on to www.thempgmarathon.co.uk