Don't really understand what they are trying to say. 2 very light small cars with very small engines return 80mpg at an unrealistic speed of 50mph on a motorway, big deal.
All I know is in 86 hours of driving with a 39mph average my 1.9TDi has returned 49mpg, which is double my 2.8Q and nearly double the 1.8T before it.
If I zero it at 60mph on a motorway I can get 70mpg but it doesn't mean a lot, the figure above is real world driving and I've made over £600 in 3 months in just fuel alone when claiming business mileage from work. Previously I was breaking even.
hang doesn't the article say they were doing the test in convoy ? If so I bet the diesel was at the front.. thus the petrol would have been saving fuel by slip streaming ?