Man falls victim to odometer scam while buying car in Chicago | How buyers can protect themselves

An old odometer scam is making a comeback that could cost you.

Paul Boroughs lives in Iowa, and says he had no idea that mileage on his pretty new car was a lie.

In November, he found an incredible deal, and paid $10,000 for a 2015 Audi A6 to a private owner in Chicago, thinking it had only 66,000 miles. But, when he registered the car with the state, he discovered truth.

"The mileage has been altered. That car has 185,000 miles on it and not 66,000 miles on it," Boroughs said.

We asked experts to run the vehicle, and they said if those low miles were real, the car could have been worth as much as $18,000.

"Was I a little bit heartbroken? Yes, because, you know, I thought maybe I was a really good car at 66,000 miles," Boroughs said.

As we discovered, it only takes minutes to cheat.

"So, go through and already selected Chevrolet HHR. This is a 2009 model," said ABC News' Steve Osunsami.

Josh Ingle repairs vehicle odometers north of Atlanta, and says thieves can quickly change an odometer reading.

"Alright, there's our kilometer value, 70,000 kilometers," Ingle said.

"And, you just tell it a new number," Osunsami said.

"That's it. Hit enter, and you'll see files 43,000 miles," Ingle said.

"Yeah, it changed instantly," Osunsami said.

"Yeah, so I mean, seconds, seconds. It takes no time," Ingle said.

"Does the car have a record of like, 'Oh, I've been tampered with?'" Osunsami said.

"Some do. Some don't. This one does not," Ingle said.

According to CARFAX, new data tells them that there are about 2.1 million cars on American roads with odometers that have been rolled back, up 7% from a year ago and 14% from two years ago. And, the cost to American car buyers is more than $1 billion each year, according to the federal government.

"So, there are sometimes organized scammers, and there are sometimes one off people," said CARFAX Editor in Chief Patrick Olsen.

Experts said the best protection is to always get a report using your car's VIN and have an independent mechanic look underneath the car before you buy.

"They can look for overly worn brake pedals, they can look for shocks and struts that may seem much more worn than that odometer reading suggests," Olsen said.

One bit of good news for someone buying a relatively new used car is that experts say that a new car or an electric car, for example, that reports its mileage online or to the Cloud, is harder to mess with, but they warn that the crooks will likely catch up there too. The best bet is to get a full report on any used car you're about to buy.