Speedo is running at 1% accuracy right now (GPS says speed is 104 km/hr, speedo says 103 km/hr). After reading I added the km/hr - wouldn't want anyone to assume I speed!
In the city the car will read 4.7 l/100 km and I will calculate 4.9 (averages based on several tanks).
On tuesday last, I drove on the highway for 650 km. The car read 4.9 l/100 km and when I filled up I calculated 4.7 l/100 km. Not bad for 104 km/hr speed on the highway. That's about 60 MPG imperial or 50 MPG US.
So the MFD seems to read high in the city and low on the highway in my car.
At any rate, it's pretty close either way. Don't be expecting "lab accuracy" from an inexpensive production car! Assume engineering accuracy is 5%, and production auto parts to be in the 10-15% range.