The Ford Mustang isn't usually the first vehicle that comes to mind when thinking about fuel-efficient cars.
But a new Mustang recently won the title of most-improved fuel economy in a U.K. gas-mileage marathon.
It wasn't a Mustang EcoBoost, the 2.3-liter turbocharged 4-cylinder model introduced to provide at least somewhat more-efficient performance, either.
Rather, the car entered in the competition was a Mustang GT, with a 5.0-liter V-8 under its hood—a truly enormous engine in U.K. terms.
In this case, "most improved" signifies the difference between the gas mileage teams achieved on the road against the vehicle's officially-rated fuel economy.
2017 Ford Mustang GT Convertible
The Mustang's performance was 75 percent higher than its official rating of 20.9 mpg Imperial (17.4 mpg U.S.) on the European testing cycle.
That result beats the previous record for fuel-economy improvement on the MPG Marathon, a 39-percent increase achieved by drivers of a Ford Fiesta ST subcompact in 2014.
With the 5.0-liter V-8, the Mustang is rated at 18 mpg combined on the U.S. EPA test cycle, regardless of whether the available six-speed manual or automatic transmission is selected.
The Mustang's achievement is a coup for Ford's U.K. division, which is importing right-hand drive versions of the iconic performance car in large numbers for the first time.
Despite significantly higher average gas prices than the U.S., two thirds of current-generation Mustangs sold in the U.K. so far have been V-8 models, according to Ford.
MPG Marathon competitors are encouraged to drive in a way that maximizes fuel economy, allowing them to achieve results better than the official ratings.
2016 Ford Mustang GT
Teams are given a series of waypoints they must stop at, but are otherwise allowed to plan their own routes.
In the 2016 MPG Marathon, the Mustang was piloted by race drivers Andy Dawson and Andrew Marriott. In a previous year's contest, they had achieved 90.6 mpg in a Ford Fiesta 1.6 TDCi diesel.
The best overall fuel economy in the 2016 MPG Marathon was achieved by a Mazda 2 1.6d Sports.
A subcompact model no longer sold in the U.S., the diesel-engined Mazda 2 achieved 88.8 mpg—although that only represented a 5.7-percent improvement over official ratings.