[Fulltiming]

It is possible to get your speedometer set to a new mileage but I don't know the process they use and it is expensive. My speedometer didn't quit working, it went into hyperdrive. The odometer portion of the speedometer would begin to record miles anytime the key was turned on. Worse yet, it would add miles like you were traveling about 50 mph. I bought my speedometer, a VDO 437152 from Dicks Speedotach.com. They charged almost $500 for the speedometer with the mileage set to match my existing odometer. It has been several years but I believe I emailed a photo of my existing speedometer to them. They sent a new speedometer to me with the mileage of my existing speedometer. Probably wasn't a financially sound move but I preferred not to have the DMV records show an incorrect mileage reading on my records. At that time, I could have ordered the same VDO speedometer from Amazon for just about half the cost with the odometer reading 0 miles.

That speedometer does have a built in function to change the ratio used to correct for speed errors based on a measured mile as others have mentioned. That is easily changed at any time.