clean carfax. >> reporter: actually, it's ne. carfax shows a potential odometer rollback a year before the dealer bought it at auction. 132,000 miles down to 68,000. >> driving around to see if we find it. >> reporter: news 4 wend undercover to that dealership. >> how did it suddenly go from that down to 68,000 miles? >> that's why there has been a mistake. >> they made a -- >> a mistake. >> a 60,000-mile mistake. >> reporter: a closer look at the carfaxhows 12 odometer readingsorted between 2012 and 2018, but the salesman kept insisting every single one of them was a astake. >> iually susan hogan from nbc 4. >> no problem, ma'am. >> reporter: at that he offered to get the owner of the dealership who asked us to stop recording, so we did. the owner, though, invited us into his office where he told us they actuallon't use carfax reports despite advertising they do. they use autocheck instead and that report shows no odometer problems onhe vehicle. take a look at this, thereno we odometer readings reported at all between 2009 and 2