I had a 1996 Ford Mondeo that showed 10% more. Then I had 2004 Ford Mondeo and it was 5% more. I sold that one and bought a 2008 Ford Mondeo and it is 5% more. My other car - 1998 Ford Fiesta - is 10% more. I also drove a 2011 Ford Mondeo and it showed more but I hadn't had it long enough to care to calculate how much exactly.

I tested all the cars except the Fiesta up to 230 km/h and the 2008 one up to 260 km/h (it's the 2.5T).

All the cars are/were German except for the Fiesta, that one is Czech.