You would have to perjure yourself on your yearly registration, when you get emissions testing you would need the tech to perjure themselves, and if you go to any mechanic that reports the mileage to the state (which some do, depending on the state) you would need them to perjure themselves too.
> Tweak the odometer and set it to 50k, sell the car
If the most recent registration says 150k and then you tweak it to 50k and try and transfer the title, the state is going to reject the application for title transfer outright. You may be charged with odometer fraud.
It may be important to note that here in France, there is no yearly registration nor emissions testing
We only declare odometer's when we sell the car. There is a technical checkup every two years which may be send that intel to the gov. Does not matter anyway : what matters is that a counter that should only be increased can be decreased, because car manufacturer do not care about any kind of IT security
Got a new car, used it for 150k km
Tweak the odometer and set it to 50k, sell the car
How could the government know I cheated ? Especially for an old car which are not connected (so even the manufacturer cannot tell)
(btw, this is used in thief networks to refurg stolen cars)