Having followed dozens of threads on this, here is my recommendations (Note - no guarantees here, just my observations)
- Try supercharging. On the charging screen, after the session, if it does not show any record of supercharging charges, or does not state that you need a payment method, the car currently probably has FUSC
- If you purchase, (assuming it appears FUSC is on the car) you will need to register the car with Tesla. After you setup your Tesla account, you will then register the car to the account. Note - you will be asked if the car is from a 3rd Party dealer or a private party puchase. From the threads, it appears that Tesla has (in the past) pulled FUSC from vehicles that were reported as 3rd Party dealer sales. FUSC for vehicles ordered prior to Jan 2017 are supposed to have FUSC tied to the VIN. The only exception is if the car was returned to Tesla and then subsequently auctioned. However, Tesla does what they want, and you can't fight them. In my case, I only reported as a private party sale. (IMHO, Tesla has no right to know where you got the car), and I only provided my registration as proof of ownership, FUSC transferred no problem. If the car has FUSC, it should transfer.
- Try to pull a carfax and see if the car ever was a lease that may have been returned to Tesla (or a trade back to Tesla). This would be a red flag that even if it has FUSC now, it may not when a new owner registers.
- Unfortunately, there really is no way to guarantee that FUSC will transfer. As you read the threads, you'll see numerous cases where Tesla has pulled it off vehicles after the car has been put on a new account. In my case, I did as I said (tested it, checked CarFax, reported as private sale) and it transferred as it should. I think the only way you can ensure FUSC transfer is if you buy from a private party, and have the seller transfer the car to you in their Tesla account. (Seems to be the most consistant). If the car is a good deal, try what I did, but keep in mind you may not receive FUSC, and you will have no leverage with Tesla. Good luck, and let us know how you make out.