Auto mechanics get a front-row seat to the worst car maintenance mistakes. From dumping boiling water on an icy windshield to filling a windshield washer fluid reservoir with engine oil, many of these mishaps have hilarious results. But every mechanic has that one story—an instance of something rolling into their shop with a side-splitting mistake—they tell over and over. So if you don’t want to tip your mechanic with a lifetime of free laughs, pay attention to the funniest car mistakes.

‘He couldn’t get all the tires to 100%’

One of my employees told me he couldn’t get all the tires to 100%….
byu/WetCmenRag inJustrolledintotheshop

Reddit’s “Just Rolled Into the Shop” forum lets mechanics share photos of hilarious car maintenance fails. One of its all-time most popular posts shows a car’s tire pressure monitoring system with four corners reading 93, 97, 96, and 94 psi, respectively. The caption: “One of my employees told me he couldn’t get all the tires to 100%…”

Obviously, most tires have a suggested maximum of 35 to 40 psi. No road tire should be inflated to 100 psi, and these ones were likely on the verge of exploding. The top comment: “Your workshop doesn’t have a bomb defusal robot by chance?” That first day on the job can be a doozy.

‘Customer states temperature gauge is reading full tank’

Customer states temperature gauge is reading full tank.

Another mechanic posted that a customer brought in their vehicle and said, “Temperature gauge is reading full tank.” It must have sounded bizarre until they fired up the car. The needle on the temperature gauge had spun so far past the red zone it was pointing at the “Full” mark on the gas gauge.

That’s one hot engine. Hopefully, the driver didn’t assume “Full” was good and keep going long enough to ruin it.

Duct-taped tire

The sidewall of your car’s tire handles a lot of heat and pressure. Most tire shops will patch a puncture in the tread but won’t touch sidewall damage. That didn’t stop one driver from trying a DIY fix.

Chris Tonn, a car expert at Reader’s Digest, recalls a customer who rolled into his shop with duct tape covering a sidewall puncture. Duct tape is great—but that’s taking things a bit far.

Garden hose engine flush

Is this internet gem true or just a troll gone wrong? You decide. On a Mustang forum, one user posted: “Make sure wen u drain ur oil u flush it out with about 20-30 gallons of water threw there and crank it over a few times, it will really help u out.”

There are so many reasons this is terrible advice. But “crank it over” with no oil is a guaranteed way to destroy your engine. Sure enough, Jalopnik spotted a heartbreaking follow-up. One new Mustang owner said they’d filled the engine with water, started it to “flush it,” and then found it wouldn’t start again.

We can only hope no real Mustangs were harmed in the making of this counter-troll post.

A very temporary tailpipe

Back in the day, a website called Boredom Therapy collected “30 Car Hacks That Are So Awful They’re Actually Kind of Brilliant.” One infamous entry featured a car muffler “repaired” with a Coke can, held together entirely with string.

This “hack” is anything but brilliant. Using an aluminum can to patch an exhaust pipe might work temporarily—but with metal wire or strapping, not string. String is flammable, and the whole setup is bound to go up in smoke after a mile or two. This driver must have just finished the fix—or had a very short commute.