No, there's no "secret odometer." I look at three things - service booklet, service/repair receipts, and carfax. The service booklet should note the date & milage of all routine servicing. This car should have a bunch of extra service - it requires an oil change once per year regardless of how few miles were driven. Inspect the repair invoices for date & milage. Lastly use carfax to insure the history aligns with what the seller is telling you. From all these sources you can put together something of a chonology of how many miles the car had on it at certain points in time. Most people use their car in a very predicatable manner - driving back and forth to work, to school, whatever. They may drive 5K miles, 10K miles, or 30K miles a year - but it's usually consistent. So I look for consistent usage during the life of the car. With enough records you can determine whether the milage is accurate. Without records, well, you gotta guess at the milage and the maintenance history.