They used a supermid to get the readings. Just because a car maxes out the FCD doesn't mean thats what its mileage is. For instance on an ideal course built to exploit the advantages of a hybrid car Wayne Gerdes maxed out the insite gauge at 150mpg. It was later reveiled that someone noticed when switched to l/100km it read 1.3 or something. This is about 180mpg or so. So don't think what a gauge reads is what your actual fuel economy is. The gauges can be maxed out.

My hydroponics experiment

You ever notice how hard it is to lip read cartoon characters?
"Crazy is what the sane call Delta Flyer"