After 12 years working as an engineer for a Fortune 500 company, I quit my management job to become an auto mechanic. I traded high heels and an air-conditioned office for boots, Dickies and grime-covered hands. The reason was simple: I was tired of feeling like an auto airhead and getting scammed by the male-dominated car-care industry.

Like many women, I felt dread each time my car’s odometer crept toward the next 3,000-mile interval. An oil change never meant just an oil change. It meant being haggled into buying a new air filter and a tire rotation. It meant being told I needed new brake pads and spark plugs — things I’d never heard of at prices that were unheard of. I’d go into a Quick Lube expecting to pay $19.95 and come out $300 poorer.

For a long time, I gave in to my helplessness. When my vehicle needed a jump-start, relying on my guy friends seemed like my only option. One of my worst moments came when the dashboard light started flashing on my two-year-old SUV. The dealer told me it had a transmission problem that would cost $1,800 to fix. The shop held my car for two weeks, and when I finally got it back, it had a totally new problem: It would shake when in reverse. On top of that, the transmission problem returned eight months later. For months, I went back and forth with the dealership, which wanted another $1,800 to fix it. From that moment on, whenever my vehicle needed major repairs or maintenance, I’d just get rid of it and buy a new one.

Most drivers have auto-repair horror stories, but women are especially vulnerable. In a 2013 survey of car owners and leasers by consumer resource site RepairPal, 77 percent of respondents said mechanics are more likely to sell women unnecessary repairs, and 66 percent believed that mechanics charge women more than men for the same services. That gender bias isn’t just a figment of customers’ imaginations. A recent study by Northwestern University found that auto-repair shops give women significantly higher price quotes than men when the customers are uninformed about market prices.

This is a major problem for the auto industry and one it has done very little to fix. Women are the industry’s top customers, holding the majority of driver’s licenses in the United States and spending more time on the road than men. They shell out more than $200 billion every year buying new cars and servicing their vehicles. Yet women hate going to the auto-repair shop even more than they hate going to the dentist, according to an AutoMD consumer survey. Why would an industry isolate its No. 1 customers?

Though the auto industry gets much of its revenue from women, it has been stubbornly uninterested in employing them. Tired of feeling ignorant and scammed at repair shops, I decided to seek out a female mechanic, but my search came up empty. I soon learned that fewer than 2 percent of auto mechanics are women. Dealerships are no better: Just 13 percent of car salespeople are women. It’s easy for us to feel misunderstood and mistreated by the auto business when we don’t see ourselves reflected in it.

I saw a major business opportunity in the auto industry’s gender gap. Becoming a mechanic wouldn’t just save me hundreds of dollars on unnecessary and inadequate repairs. It also would allow me to save other women from the same fate. At 31 years old, I started taking night classes at a community college and worked weekends at a repair shop for free. After two years, I earned a diploma in automotive technology and ended my engineering career to launch Girls Auto Clinic in Philadelphia.

For the past couple of years, I’ve been holding free workshops in parking lots, garages and auto-repair shops to educate women about the basics of car care so they’re equipped to ask questions and negotiate prices with mechanics and salesmen. Companies and women’s groups, including Girl Scout troops and car dealerships, have hired me to talk to their employees and members. I show them what the various parts of cars do, when those parts need to be serviced, what fluids need to be changed and other aspects of what’s under a vehicle’s hood. I even accompany women to dealerships and repair shops to haggle with the men trying to sell them cars and parts. It’s amazing how often salesmen don’t know the answers to my questions about a used car’s upkeep and how quickly they’ll knock $500 off the price when you tell them you know the vehicle is due for major maintenance. When a woman can negotiate, it’s empowering.

But knowledge isn’t women’s only barrier to getting equal treatment by the auto industry. The business suffers from pervasive sexism that cripples even the most informed and capable women. Cirina Johns, a technician I now work with, struggled for years to gain the respect of the male colleagues and bosses who assumed she wasn’t strong or capable enough to work on big trucks and more challenging jobs. It’s a common story for women who work on cars. Most of us do it on our own because we can’t find shops that will give us a chance or treat us as equals. Even when I was in school and looking to work for free, a lot of shops told me no. When I started planning to open a repair shop in Philadelphia to be staffed by female mechanics and cater to female drivers, Cirina immediately moved from New Jersey to join me.

Recently, I visited a technical high school to discuss what it’s like to be a woman in the auto-care industry. All of the students were boys, and they made clear that they were skeptical of my credentials. They looked at my hands to see how dirty they were. They quizzed me on my knowledge of car parts and mechanics. Even after I passed their tests, the boys told me that I was too much of a distraction to work with men. They were still teenagers, but that kind of mentality is what discourages girls who are interested in cars from going into the business — and fuels the industry’s gender disparities.

Making auto-repair shops and car dealerships safer spaces for women is just good business. But the men who control the industry aren’t the only ones who can force that change. As their biggest customers, women have a lot of power to disrupt this industry. We can arm ourselves with the knowledge to protect both our wallets and our vehicles from overpriced parts and unnecessary repairs. We don’t have to be auto airheads.

Twitter: @girlsautoclinic