Where does the odometer reading go?
On the back of the title, both of you signing
If the vehicle is model year 2011 or newer and under 20 years old, write the odometer reading on the back of the title — and both you and the buyer must sign it. In that year range a lost title has to be replaced before you sell, because the reading has to go on the title itself. No disclosure is needed for model year 2010 or older, vehicles over 16,000 pounds gross vehicle weight rating, vehicles that are not self-propelled such as trailers, vehicles made without an odometer, Class I ATVs, or snowmobiles.
Source: Oregon DMV, Buying or Selling a Vehicle; Odometer Disclosure; 49 CFR 580.5(c)