My first car had a broken speedometer. It was a "hand" style like a clock. Instead of moving to the speed, it would spin 365 degrees. The faster the car went, the faster it would spin. Turns out, I acclimated to it and generally knew what speed i was going (relatively speaking).
The lesson, I think, is everything is relative. Even a dashboard with flawed data that is "consistent" can highlight anomalies. And often, that's all you really need out of them. (Or the lack of anomaly)
“Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience.”