In the United States alone, roughly 750,000 auto mechanics spend long shifts diagnosing, repairing, and preventing motor vehicle problems. But thanks to some stereotypical portrayals in media and a complicated vocabulary of car parts, drivers can sometimes feel like their lack of understanding may prompt technicians to take advantage of them. That's not the case, mechanics say—the techs are here to help. To get a better idea of what their job really entails, mental_floss spoke with several mechanics at both independent repair shops and dealerships. Here’s a glimpse at what goes on after your car goes in.

1. THEY WISH YOU’D STOP WIPING BOOGERS ON YOUR SEAT.

A car can often resemble someone’s mobile living room, full of decorative accents, music, and occasionally dried snot. Charles, a mechanic who works at a Volkswagen dealership and runs The Humble Mechanic blog, says he’s seen his share of nose gold while working on vehicles. “People seem to like picking their nose and wiping it on the seat,” he says. To do a proper job, techs would prefer you bring in your vehicle without bodily fluids or trash inside. “Sometimes there’s a bunch of dirty clothes over the spare, or fast-food wrappers on the floor that we ask customers to remove. A lot of cars are clean, but people can be gross.”

2. THERE’S A SPECIAL BOOK THAT TELLS THEM WHAT TO CHARGE—EVEN IF IT’S TOO MUCH.

Ever walk away feeling like you’ve overpaid for a repair? It’s possible, but it’s not entirely the shop’s fault. Most every mechanic working on a flat rate (as opposed to a per-hour rate) references an industry trade manual that estimates how long a typical repair should take. If you’ve paid, say, $200 for a two-hour job that an experienced mechanic can get done in 30 minutes, you're still charged by the book—and you don’t get a refund.

The auto tool industry may share part of the blame. “The way it becomes unfair is when a mechanic buys a new specialty tool that may cost $300 but that pays for itself quickly,” says Ryan, a former mechanic in Colorado. “It means they can do the job in less time, but the customer still pays for full time.”

3. THEY CAN FIND MICE AND SQUIRRELS STUCK IN YOUR AXLES.

Depending on what part of the country you live in, a car's warm underbelly can be attractive to rodents and other animals. Charles has seen acorns socked away under hoods and once pried a squirrel from the front of a grill. “The biggest thing we see [in North Carolina] is chewed wires from mice,” he says. “They’ll make a nest in the air box. I’ve also had to clean deer guts off.” If you’re going to be storing your car for an extended period of time, Charles says some kind of rodent deterrent spray might help.

4. THEY MIGHT RUN SOME ERRANDS IN YOUR CAR.

While few mechanics actually take vehicles out for joy rides, the fact that they don’t get paid for the time it takes to test drive one means your spotless new Honda might develop a surprise ketchup stain on the driver’s seat. “Basically, every vehicle needs to be driven to make sure the problem is resolved,” Ryan says. “If you’re headed out to lunch and you need to confirm that, it makes sense to drive it down the road.”

5. THEY MIGHT RESCUE YOU IN A ROADSIDE EMERGENCY.

While their individual morality mileage varies, many mechanics feel duty-bound to pull over when they spot a stranded driver. “I do a lot of highway driving in the winter and the rule of thumb is if you see someone stranded on the highway, you stop and check on them,” says Ryan M., a mechanic in Winnipeg. “I've also pulled lots of vehicles out of ditches and off curbs.”

6. DEALERSHIPS HAVE ACCESS TO RESOURCES THAT PRIVATELY-OWNED SHOPS DON’T.

If you’ve ever wondered whether you should take your out-of-warranty vehicle in for a repair at a cheaper, locally owned shop over the dealer-branded shingle, here’s something to keep in mind: Many of those smaller outfits can’t afford the kind of information provided by car manufacturers to help successfully diagnose and treat a problem. “We’re able to go deep into the Volkswagen brand,” Charles says. “There are a lot of resources we have access to that an independent place wouldn’t. We can get access to the car’s engineers if we need that. The brand is an ally. A small shop isn’t going to spend $15,000 a year [for that data] to specialize in one kind of car. Once it’s outside their scope of knowledge, it makes more sense to go to a dealer.”

7. YOU’RE TECHNICALLY NOT ALLOWED IN THE GARAGE. EVER.

You’ve probably heard advice about making a mechanic show you a defective part to guarantee they’re not simply making up work to do. That involves a trip beyond the forbidden door marked “Do Not Enter.” But according to Ryan, you’re not actually supposed to be back there for any reason. “Insurance companies don’t want customers in the garage, ever,” he says. “It’s not that dangerous, but it’s not supposed to happen.”

8. THEY SOMETIMES MAKE THEIR OWN TOOLS.

While mechanics start out by buying their own tools—some even investing tens of thousands in supplies—there will always be instances where they’ll need to improvise. “A tool might be missing, or not put back in the right place,” Charles says. “Or a company just might not make what you need. I have a whole drawer full of cut-up sockets and wrenches. Making a custom tool is fun.”

9. THEY USE A COOKIE SHEET TO STAY ORGANIZED.

While cell phones have become handy to help keep track of how a part needs to be re-assembled, some mechanics still like to stay organized by laying out pieces in a specific order. “If I'm working on a vehicle I've never seen before, and it's a complicated job or a job spread out over multiple days like a transmission rebuild or something like that, I'll take a cookie sheet and magnets and lay things out spatially to stay organized,” Ryan M. says. “You can also mark parts with a Sharpie.”

10. THEY DON’T ALWAYS PERFORM EVERY LITTLE TASK.

Cars brought in for maintenance are supposed to undergo a litany of small adjustments, but that laundry list can sometimes get skipped over depending on how pressed for time your technician is. “Stuff like lubricating door hinges or latching mechanisms gets missed all the time,” Ryan says. “It doesn’t affect performance at that moment, but it can over time.”

11. THEY’RE IMPRESSED BY DRIVER MACGYVERS.

Not everyone can rush to a repair shop when a problem crops up, necessitating some improvisational skills. “I once had someone rig up a dipstick stop with a beer bottle cap,” Charles says. “Someone else used a chewing tobacco lid for a coolant cap. And we had someone else keep the driver’s door shut by rolling both windows down and securing it with a belt.” Less impressive: tin foil in place of a gas cap.

12. IT’S OK TO MAKE SILLY NOISES FOR THEM.

Cars make all kinds of odd sounds, which means drivers are often left to try and replicate them. Mechanics prefer this over you trying to explain the noise verbally, no matter how silly it makes you feel. “I'd rather hear a funny noise come out of you than waste time trying to figure out what you mean by ‘buzzing, but it's like squishy if that makes sense,’" Ryan M. says. “Make the damn noise!”

13. SEARING HOT OIL BURNS ARE NO FUN.

A garage is a seriously hazardous hub of activity, with mechanics working alongside one another tending to multi-ton vehicles raised above their heads. While major injuries are uncommon, dealing with chemicals is a common source of pain. “Hot coolant and hot oil are the two main things I’ve seen people get hurt the most with,” Charles says. “That’s a weekly occurrence.” Other pitfalls: dropping heavy wrenches on your toes, or having someone fail to [use] the brakes before backing out, running down a co-worker. “A guy broke his arm that way.”

14. THEY MIGHT WATCH YOUR KIDS GROW UP.

The best mechanics, Charles says, play the long game. By being attentive and engaged with customers, they’ll often see their clients' offspring returning with cars of their own. “A kid could come in at 10 and all of a sudden he’s 16 with his first car,” he says. “Then he’s in college and his mom wants a new car. I’ve had families of people with four or five Volkswagens and I’m working on all of them." That personal touch also extends to tokens of appreciation. "Sometimes I even get cookies.”

15. THEY LIKE TO GO HOME AND WORK ON CARS SOME MORE.

Surprisingly, a number of mechanics don’t get their fill of greasy hands and wrench lacerations during the day. According to Charles, having a personal vehicle to tinker with is an entirely different experience than working on a customer’s ride. “Wrenching on cars all day at work is similar to working on an assembly line,” he says. “Car comes in, gets fixed, goes out. Car comes in. At home, it’s 180 degrees from that and relaxing. We all like to tinker.”

All images courtesy of iStock.