Boffins call for "gallons per mile" car ads

A simple change in the way car firms calculate fuel efficiency could help carve $1,000 a year (£507) off drivers' annual fuel bill, according to a new US report.

Researchers at Duke University in North Carolina claim that working out "gallons per mile" rather than the traditional "miles per gallon" will give motorists a far clearer idea about the amount of fuel they are using each year.

They say that a car offering a five gallon per mile improvement in efficiency would save the same amount of fuel as a car that yielded a 10 miles per gallon improvement. Yet the researchers found that most people could not identify which method achieved the better fuel efficiency, with the majority finding it easier to work out efficiency when it was expressed in gallons per 100 miles (161km).

"The reality that few people appreciate is that improving fuel efficiency from 10 to 20mpg is actually a more significant saving than improving from 25 to 50mpg for the same distance of driving," report co-author Richard Larrick, a management consultant at Duke University’s Fuqua School of Business said.

Larrick – along with co-author Jack Soll – is now calling on all car manufacturers to start detailing fuel efficiency in terms of gallons per 10,000 miles driven – the average annual driving distance in the US.

The news comes as the UK government last week issued new guidance tightening rules forcing car manufacturers to include fuel efficiency and carbon emissions data on all car adverts. Previously billboard adverts had been exempt from the legislation, but now the government has said that they too are covered by the rules and must feature clear fuel efficiency and carbon emission data.