How’s this for a summer road trip — 14 countries on one tank of diesel

2015 Audi A6 TDI Ultra "Record Road Trip"

What’s your idea of the ultimate road trip? How about traversing 14 countries in 28 hours? And how about doing that on just one tank of fuel?

Audi accomplished this feat last week using a diesel-powered A6 TDI sedan. The car was driven from The Netherlands to Hungary on a single tank, setting a Guinness World Record in the process.

Auto journalist Andrew Frankel and race driver Rebecca Jackson drove for nearly 28 hours, covering a total of 1,158.9 miles though The Netherlands, Belgium, Luxembourg, France, Switzerland, Lichtenstein, Austria, Germany, Italy, Slovenia, Croatia, Bosnia, Serbia, and Hungary.

The car was not modified in any way, and Audi reckons it achieved an average of 75.9 mpg over the duration of the trip. That’s significantly higher than the 56 mpg combined this Ultra model is rated for in Europe.

Audi reserves the “Ultra” designation for the most fuel-efficient version of a given model. While the German carmaker does offer several TDI diesel models in the U.S., the Ultra versions are only sold in Europe at the moment.

The A6 Ultra uses a 2.0-liter turbocharged four-cylinder engine, which is available with either 150 horsepower or 190 horsepower. So while efficiency may be one of this model’s virtues, power and speed certainly aren’t.

The 150-hp version takes takes 9.5 seconds to reach 62 mph from a standstill, while the more-powerful model can do the job in a more respectable 8.7 seconds. Not that there was any particular need for speed on this economy run.

Even though they finished the trip in just over a day, Audi says the two drivers were slowed down considerably by traffic, a crash, and a closed tunnel that required an unplanned mountain detour. Imagine what their time would’ve been without those diversions.

While the phrase “your mileage may vary” applies to any fuel-economy-related claims, this stunt does show just how good diesels can be for long stretches of highway cruising. Just as hybrids are most at home in city driving, diesels love the highway.