Can you scan a car to get the true mileage?
The engine computer on some vehicles may store a fuel mileage estimate. The later model Dodge Rams with the Cummin's diesel store estimated gallons of fuel used and miles driven.
If you want to find out the Rent A Car (RAC) mileage, when you go to rent a car, the car rental place will check the mileage before you leave with the car. The mileage will also be checked when you return the vehicle. There is no reason to book an RAC mileage check unless you plan on renting an automobile.