I must second to the bit of scepticism expressed above. Not to MPG record of that particular car (seemingly supported by whole team along the journey), but also to posted MPG rating (but I admit it is very good).
All European sold cars (afaik) are rated according to NEDC (New Europen Driving Cycle), not EPA methodology.
Wikipedia has a nice writeup here:
https://en.wikipedia.org/wiki/New_Eu..._Driving_Cycle
NEDC is notoriously known to be far off the real-world performace (sometimes as much as 20%) - so if the official stats says 61.9 U.S. mpg, real figures would be around 52 U.S. mpg)
(I am no expert, this is common experience. For instance my car has official consumption rated at 4.8 l/100 km (49 MPG) and I almost managed to achieve it (using all the tricks i can safely use during my daily driving). My father with similar car gets around 5.7 to 6.1 l/100 km (41.3 to 37.3 U.S. mpg)
- so nothing wrong againts the car nor the record. Just take the impressive MPG numbers of european cars with grain of salt.