How Auto Mechanics Can Rip You Off, and How to Avoid Being Taken for a Ride

... and how drivers can avoid being taken for a ride.

ByABC News
September 12, 2014, 11:34 AM

— -- intro:Have you ever gone to an auto repair shop for an oil change, only to have the mechanic say your car needs a new transmission? Has the “check engine” light come on, and suddenly the mechanic says you need expensive new engine parts?

One seasoned auto mechanic is warning consumers to be well-versed in how a car works to avoid being ripped off at the auto repair shop.

“Joe,” who has been a mechanic for 40 years, agreed to reveal the secrets of his trade to ABC News' “20/20” on the condition that his identity would remain concealed.

He said some mechanics may try to squeeze more money out of customers by doing unnecessary repairs. What drives mechanics to cheat or push unnecessary repairs, Joe said, is the tiny profit margin at many repair shops. Most mechanics are honest, he said, but many are pressured by their bosses to perform unnecessary work.

“The shop has to stay in business,” Joe said. “There are pressures to do things that maybe you wouldn’t do normally.”

Joe admitted that he has used shady tactics, himself, in the past.

“I’m ashamed a bit to admit it, but when your boss tells you ... 'Either you do it here or the door’s right there,' what are you going to do?” he asked.

The Automotive Service Association says the majority of the service repair industry is ethical and only charges the consumer for necessary work.

“20/20” went undercover at several auto repair shops in New York and New Jersey to see if mechanics would add unnecessary repairs and fees to service a “20/20” producer’s car, which had been given a clean bill of health by two licensed mechanics beforehand.

One of those licensed expert mechanics was Giuseppe Mendola, owner of AutoTech Diagnostic in College Point, New York.

“If they found a problem with this car, it would probably be a problem they invented or that didn’t exist at all,” Mendola said.

quicklist:title: 1. Adding on to 'Gravy Work'text:There are special names mechanics use for questionable repair practices, Joe said, such as “gravy work,” which, he said, means billing the customer for more time than a repair job actually takes.

“Most shops will charge you an hour and a half to two hours to turn the rotors and put pads on it,” Joe said. “If you’re good and got good equipment, you can do it in 20 or 30 minutes. ... That’s gravy.”

quicklist:title: 2. Doing a 'Wallet Flush'text:The so-called “Wallet Flush,” Joe said, is where a routine oil change can turn into something much more expensive.

“An $18 oil change -- well, they lose money on that,” he said. “The idea is to get you in so they can sell you the coolant flushes, trans flushes, power steering flushes. ... That’s where the money is.”

quicklist:title: 3. Billing for Work That Was Never Donetext:Joe said it’s not unusual for mechanics to bill for work they don’t even perform, such as saying they installed a new air filter without actually touching it.

“Some [air filters] are difficult to change, and it’s real easy to charge for it and not put it in,” he said. “And you would never know because you couldn’t go get it.”

quicklist:title: 4. Jacking Up Repairs Based off the 'Idiot Light'text:One of the most common, and profitable, ways to jack up a repair bill is exploiting fears over the “check engine” light, affectionately known by some in the trade as the “idiot light,” Joe said.

“The check engine light will direct you to a failure code,” he said. “Guys kind of have the phrase where every code deserves a part.”

“20/20” put the “idiot light” tactic to the test. Before heading out undercover, “20/20” had expert mechanic Audra Fordin purposefully unplug a cord to disconnect the mass airflow sensor in the engine of a “20/20” producer’s car, something that would be quickly detected and easy to fix. Both Fordin and Mendola deemed the car perfectly fine otherwise.

One repair shop in New Jersey fixed the cord issue in 15 minutes without even charging our producer -- though ABC News' expert mechanic say it would be reasonable to charge between $50-100 to diagnose the problem. The manager at a different repair shop in New Jersey also just plugged the cord back in, but then told our producer the light was on because the mass flow sensor needed to be cleaned. He recommended a fuel system cleaning for $99.

A mechanic in New York also fixed the cord problem quickly but told our producer she needed to replace the entire mass air flow sensor, a cost of more than $300. He then offered to take the sensor apart and fix it for $190. For that $190 fix, a “20/20” hidden camera video showed the mechanic just sprayed and rinsed the outside of the engine.

“The light was definitely on because of the sensor,” Mendola said. “And plugging it back in should have the solved the problem. ... I can give you an example. If you came home and your lamp wasn’t working and you realized, ‘Hey, somebody unplugged it from the wall,’ you wouldn’t go out and buy a new lamp. So basically, all you had to do was plug it back in and you’d be fine.”

quicklist:title:5. BONUS: How to Avoid Being Ripped Offtext:“If you go to a shop, and they ... spring you up for all this stuff, go find another shop,” he said. “Ask your friends, ask coworkers. ... Try to find a reputable shop that you can build a relationship with, and they will take care of you, and that’s key.”

Also, he added, just read the owner’s manual.

“People don’t read the owner’s manual," he said. "They don’t know how to open the hood half the time. ... I honestly don’t understand what they expect out of the car if they don’t know anything about it.”

Marty Guerrero, 50, of Los Angeles, admitted she didn’t know anything about cars when she took her red Mustang into a mechanic when it wouldn’t start. She said that was all the mechanic needed to know, to take her for a ride.

“He ended up wanting to charge me about $1,000 for services, and it turns out all my car needed was a battery,” said Guerrero. “And the only reason I busted him was because my car wouldn't start two days after I picked it up. After he supposedly fixed it, it wouldn't start.”

What should have been an $80 battery replacement suddenly became a very expensive problem for Guerrero.

“When I think about it now I feel like a fool,” Guerrero said. “I really got taken.”

But Guerrero battled to get her money back from the mechanic and won. She even enrolled in auto repair classes and is educating others through an e-book she wrote, named, “Exposed: Auto Repair's Dirty Little Secrets to Rip You Off!”

“I ended up writing a book because I wanted to share all this knowledge with people,” Guerrero said. "It really makes me angry that these mechanics are taking advantage of women. ... They primarily cheat women because they think we don't know.”

Guerrero had a message for the mechanic who she said ripped her off: “I got you,” Guerrero said. “You thought you were slick, but I got you.”