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13 Worst Car Tips Mechanics Have Ever Heard

Updated: Mar. 12, 2024

There are countless self-styled experts who preach some truly terrible car repair advice. Here are the worst myths we've ever heard—and the facts to follow instead.

car mechanic working below a bar
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Bad advice, good alternatives

Aside from your home, a car is likely the most expensive thing you’ll ever buy. It only makes sense that you’d try to keep it in tip-top shape by following the experts’ car maintenance tips and car hacks. Unfortunately, some people try to cut corners when keeping their cars running. Others end up on the wrong end of some really terrible advice. We’ve heard some doozies, and so have the pros. Here are some of the worst things they’ve heard—and why they’re such bad ideas. If it’s time to replace that old clunker, however, check out a list of the best cars for 2021.

car's windshield rain wiper.selective focus.

Saving money by using water instead of washer fluid

Windshield washer fluid isn’t expensive—usually under $5 per gallon. It’s formulated to clean better and have a lower freeze point than water. Still, some people try to get by with the stuff from the tap. Kevin Coyle, general manager of Carvana’s inspection center near Philadelphia, says that “if [washer fluid is] replaced with water, you risk clogging the reservoir and associated hoses.” It can do even more damage if you live in colder climes. “In low-temperature climates, the reservoirs will crack when the water freezes and expands.” Do right by your car and only use washer fluid in the reservoir—and update to the best windshield wipers when your old ones stop working properly.

A technician in the workshop exchanges oil

Skipping oil changes because you only drive short distances

Most drivers know that there is a recommended mileage interval for oil changes. Some experts recommend a 3,000-mile interval, though it’s best to follow the recommendations for your specific type of car. Lauren Fix, aka the Car Coach, suggests you “change your oil per the owner’s manual service schedule—it’s always based on miles driven and not time.”

That said, oil does break down over time, so even if your car sits for long intervals, you should still change it regularly. If you only drive short distances, the engine doesn’t have enough time to warm up properly, which is hard on the oil and can cause it to break down.

Putting money into a beater because it’s a classic

We’ve all heard about classic muscle cars that sell for six figures or more. The family sedan you’ve been driving for 20 years won’t be on a classic car auction website or TV show anytime soon, so don’t waste your time and money repairing a beater that’s about to die in an effort to make millions someday. An anonymous technician spills about a client who won’t give up on her 1992 Saab: “I keep begging her to stop getting it repaired. She’s spent thousands and thousands on it. The parts keep getting more expensive because the company no longer exists,” the technician says. “But she’s convinced it’ll be worth a ton if she holds onto it long enough because it is ‘rare.’ It’s not rare, and she could probably trade it in for a couple hundred bucks at most.” If you find yourself in the same situation, cut your losses; sell the clunker and invest in a new car that doesn’t require regular repairs.

driver gripping steering wheel shaking
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Ignoring funny sounds and feels

If you hear squealing, rattling, scraping, or crunching noises coming from your car, some experts might suggest driving for a while to see if they persist. That’s a big mistake—these sounds are all signs that something is wrong. For example, if you hear a squeal or feel the steering wheel shake when braking, it’s a sign that your brake pads are probably due to be replaced. According to Fix, replacing the brake pads costs an average of $200. “If you wait until they are really bad, you’ll need more brake repairs and it becomes a $2,000 brake job,” she says.

High Performance Tire and Rim
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Fixing badly damaged tires instead of replacing them

Your tires are critically important to your safety, so you want to make sure you have the best, safest tires on your car. As a car expert, I’ve seen so many attempts at cheap repairs, and I’m somewhat ashamed to say, I attempted a few when I was younger.

The sidewall of your tire is the part of the tire between the wheel and the tread. Maintaining its structural integrity is important—so much so that most reputable tire shops won’t repair a tire with a puncture on the sidewall and the Tire Industry Association recommends against repairs to anything but the tread of the tire. Still, when I worked in a tire shop, I actually saw people drive into the shop with duct tape covering a sidewall puncture. Don’t risk it. It’s time for a new tire.

Professional mechanic checking car engine

Flushing your engine with water

A post on car blog Jalopnik details how a guy with engine troubles decided to run water through the engine “to make sure all the bad stuff got out.” A few minutes later, his car started shaking, turned off, and refused to turn back on. Let this be a lesson to you: Don’t flush your engine with water! You’ll have the most sparkling frozen engine in the junkyard. On a happier note, find out the weird but cool car features you might have.

defrosting car windshield
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Using hot water to defrost a windshield

If you’re in a hurry on a freezing morning, you might think it’s a good idea to use boiling water to get rid of the ice on your windshield. It sure sounds easier than scraping off chunks or waiting for your car’s defrost to do its job. But the thermal shock will “cause the glass to expand and contract very quickly,” according to Coyle. The result: a chipped or cracked windshield. Instead, start the car and use the defroster to gradually warm the glass from the inside, and use a good ice scraper to chip away at Jack Frost’s leavings. You might also consider leaving your wipers up overnight to keep the rubber blades from freezing to the glass.

 Man Checking Car Tire Pressure With Gauge

Setting your tire pressure based on the imprint on the tire

Tires are the most important safety feature on your car. After all, they’re the only things touching the road. Keeping the tire pressure in the proper range is critical for safety and longevity and is often the first item on a road trip checklist. But be careful about using the right numbers to guide your tire pressure. There’s a pressure rating imprinted on the side of each tire. That, however, is the maximum pressure the tire is designed to hold. Never use that number as a guide when setting your tire pressure—it can lead to handling problems and possibly a blowout. “Use the tire pressures on the sticker inside your driver-side door as a guide,” says Fix. “Use a digital pressure gauge and check the tires when they are cold to get an accurate reading. This extends tire life, increases fuel economy, [and] improves handling and safety too.”

Car air conditioning vent

Not sweating an overheating engine

Hilarious Twitter account @badcaradvice offers this terrible fix: “When your engine is overheating, turn up your AC to chill that sucker down!” As you can probably guess from the username, that is indeed some bad car advice. It’s actually the opposite of what your car needs: Turning on your heater may help tame the engine temperature, but the safest thing to do is pull over and contact roadside assistance.

rain washing over car exterior
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Waiting for the rain to wash your car

You may be able to deal with the eyesore that is a car covered in dirt, pollen, and bird droppings, but you really shouldn’t. It’s about more than enduring a dirty car until the rain washes away the mess. “When you let your vehicle go long periods between washes, you not only doom yourself to driving around in a dingy car, but your neglect can dramatically reduce your car’s value,” says Fix. “Built-up dirt can diminish paint, encourage rust, and allow pollutants to become embedded, which can enhance scratches and dings.” Maintain your car’s exterior with regular washings—every couple of weeks. And yes, you need to wash your car in the winter, as well.

a silver car is washing in soap suds
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Using dish soap to wash your car

Dish soap is great for your pots and pans because it strips all of the gunk you don’t want to be eating off the surface of your cooking tools. But your car’s paint probably has wax and other protectants to keep it shiny. Fix says dish soap dulls the finish and requires a visit to a detail shop to fix the damage done to your paint. Listen to Fix and professional car detailers, who recommend always using a product meant for cars.

jerry-rigged exhaust pipe on a car

Creating a jerry-rigged tailpipe

In a list of terrible automobile DIY projects, Boredom Therapy posted a photo of someone’s homemade fix for a rusted tailpipe: They patched it with a Coke can and string. Avoid this or any other do-it-yourself fix. Exhaust pipes get incredibly hot, so that’s a fire waiting to happen. Instead, take your busted tailpipe to a repair shop. If cost is an issue, choose your next vehicle from this list of car brands that cost the least to repair.

Ignoring dashboard warning lights

Your car’s dashboard is there to give the driver information about what is going on with the car. If a yellow or red light appears on the instrument panel, it’s because there is something wrong. When I worked at a car repair shop, I even saw some cars with tape on the panel to cover up the annoying warning lights. This is a bad idea because you could be making the problem worse by delaying the inevitable. A check engine light, for example, could be a simple fault, like a loose gas cap, or an impending failure that could cost lots of money to repair. “They won’t go away,” says Fix, “and the resulting damage to your emissions system and engine could be very expensive.”

Additional reporting by Joe McKinley.