We must distinguish two things here. Do I want to read an exact speed indication while driving? Or do I want to know exactly how long the distance travelled is in miles or kilometres?
As I have experienced, the relationship between these two objectives is fixed and unchangeably programmed.
So if you want to see the exact speed while driving, the odometer does not count enough kilometres driven.
If you want to see the exact distance, you will see more speed on the speedometer than it is while driving. This is because the speed indicator needs to show a little more than is. Strictly according to the law, the odometer has to be calibrated, and consequently the speedometer shows slightly higher values. Of course it should not be too much.
