'He had put 3-4 CASES of oil in the motor': 20 Mechanics share the surprising cars customers brought in to them

Author image for Remy Millisky
Remy Millisky • Writer and Editor
Mar 31, 2025 11:00 AM EDT

When that check engine light flashes on, it's time to take your car to the shop once again. I mean, you can put it off for a week or 6 months as some drivers do, but the longer you wait, the worse off your car is going to be. Sometimes you just need an oil change, or maybe your tire pressure is uneven. You know it's going to cost you a big chunk of cash… but waiting until your car is smoking on the side of the road to take it into the shop is just going to cost you more. 

Some people simply refuse to let other people touch their cars, either because they want to save money, they think they're a "car person," or they don't trust other people with it. They crack their knuckles, roll up their sleeves, and… pour water straight on the motor. Or they pour oil into the gas tank. Or they overfill their tires to the max. There are plenty of ways you can turn a quick fix into a bricked car, and the people below did just that before finally turning the job over to a qualified mechanic. 

Next, read about these folks who are red-faced with embarrassment after having some awkward work encounters, like one worker who "accidentally called my boss 'Mom'."

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  • 01
    Cheezburger Image 10487356416
    via Kenny Eliason on Unsplash+

    The image does not depict the actual subjects of the story. Subjects are models.

  • 02

    "Mechanics of Reddit, what's the dumbest thing you've seen someone do to their vehicle?"

    Chum731 My old mechanic had a guy come in with a Ford Probe. He claimed it was "low" on oil. They take the dipstick out and the whole stick has oil on it. He checks again with the same result.
    via u/Chum731
  • 03
    The guy took the oil cap off and looked into down into the hole and said see it is "low" He had put 3-4 CASES of oil in the motor trying to fill the entire block up
    via u/Chum731
  • 04
    thedreamlan6 The previous mechanic didn't know how to patch an exhaust leak, and had tried to weld a ROCKSTAR CAN around the leak. The leak caused the 2nd oxygen bank to fail, which is why they tried to patch it with the can. Not a week later the bank read a failure again.
    via u/thedreamlan6
  • 05
    zerogear5 This probably won't be the worst one in this thread. I used to know a 30 year old who would put the car air freshener duct taped outside the exhaust, kind of just dangling in front of the opening. His logic was it makes the exhaust smell better for pedestrians.
    via u/zerogear5
  • 06
    Ejgee Had a customer once who had their oil light come on and couldn't figure out how to top the oil up. He thought it might have worked like his boat motor so he poured a jug of oil in his fuel tank.
    via u/Ejgee
  • 07
    neightwulf Not a mechanic, but former service writer. Woman comes in for an oil change, some common mini van, nothing out of the ordinary. Walked by the van while it was up on the rack, and noticed one of the tires was nearly bald in the middle, cords showing -- textbook over-inflation.
    via u/neightwulf
  • 08
    I check the tire pressure, was well over-inflated. Then looked around the vehicle -- two more tires were in exactly the same state, over-inflated and showing damage from it. The fourth was a bit under-inflated, no glaringly obvious tread wear. Pointed it out to the customer when she came back, asked if there's any reason three tires would be
    via u/neightwulf
  • 09
    over-inflated. Long story short, she was occasionally seeing a "low tire" light on the dash (no indication of which tire, just "low tire"), told her husband, and he just aired up all four tires. Happened again, "fixed" the same way, rinse and repeat.
    via u/neightwulf
  • 10
    So over time they kept the tire with the leak going, but managed to ruin the other three. Buy a tire pressure gauge if your car doesn't give you per-tire pressure readings ...
    via u/neightwulf
  • 11
    fullhalter I wrench on bikes, not cars, and at least once a month we have someone come in that put chain lube or grease on their brake rotors because they were squealing, and now wants to know why their brakes aren't grabbing.
    via u/fullhalter
  • 12
    robbins549 I was working at a performance shop at the time ~2010. Golf GTI comes in for lack of power and throwing check engine codes for underboost and several for fuel trim management conditions. Did the typical process of checking the turbo waste gate operation, pressure and smoke tested the charged side of the turbo system for
    via u/robbins549
  • 13
    leaks, tested fuel pressures, all checked out. Removed the intake side from the turbo to inspect for rips in the rubber boot, all good. Looked inside the intake boot and this moron bought one of these turbonator gimmicky things and put it inside the intake. It had turned completely on it's side and was restricting ~80% of the air flow. Removed the "obstruction" and motor operating values
    via u/robbins549
  • 14
    returned to normal and power was restored. Did not feel any guilt that this idiot had to pay a few hundred for me to diagnose and remove his awesome diy performance mod.
    via u/robbins549
  • 15
    Cheezburger Image 10487369472
    via Tim Mossholder on Unsplash+

    The image does not depict the actual subjects of the story. Subjects are models.

  • 16
    Filwathen Completely fill their engine with oil and wonder why it's smoking and then locked up.
    via u/Filwathen
  • 17
    Missanonna The list is long. Removing PCV hose, assorted vacuum lines, O2 sensor, etc thinking they are going to get better performance. Cutting a wire under the dash to hook up a stereo. Then bringing the car to me to fix the tail lights. Pouring
    via u/Missanonna
  • 18
    3 quarts of oil in but the dipstick still shows low because they put the oil in the radiator. Putting gasoline in a diesel truck...again.
    via u/Missanonna
  • 19
    mi... I bought my car off a guy for $785. For all intents and purposes it worked fine, but the guy said that it overheated almost daily. 1999 Nissan Sentra, manual, 135K miles. If it didn't overheat it would have been closer to $3-4K, maybe even more. I bought it anyways, cause I could try fixing it and cause I was desperate for a car (my old
    via u/mikhela
  • 20
    one di d and I lived 10 miles from work). So I brought the car home (the guy filled the radiator per an agreement we made), and the overflow tank was already empty. I started feeling along the coolant piping, and when I came to the thermostat sensor housing I could stick my fingernail inside the gap. My fingers came out soaking wet with coolant.
    via u/mikhela
  • 21
    Went to a parts store, spent $10 on a housing gasket, $3 on some liquid gasket, and $50 on new oil, a new oil filter, a new air filter, radiator cleaner, and coolant. Spent an entire day putting that gasket in (the reason it took so long is a frickin story and a half that was all about Murphy's law), changed the oil, cleaned out the radiator, and I haven't had any trouble since. All in all, a perfectly working car for
    via u/mikhela
  • 22
    about $850. I kinda feel bad for the dude who sold it to me.
    via u/mikhela
  • 23
    Ismrzz Did a co-op at a shop back in high school, guy complains about how his car doesn't sit straight. We pull it in and don't even need to put it on the lift to realize that he has 17 inch rims on one side and 15s on the other. Took me about 45 minutes of explaining to him why cars aren't made like that before he told us that he'd be taking his business
    via u/Ismrzz
  • 24
    elsewhere. On a side note the side with the 15s were 100% bald, like racing slick bald and everything in that car was falling to pieces. I have too many stories of sh I found in peoples cars there, but this one has to be my favourite.
    via u/Ismrzz
  • 25
    Ze... Worked as a car cleaner at a dealership one summer in high school. Guy towed in a relatively new, top of the line Corvette he had bought there sometime before I started. He was p ed that it had di d on the road and been running like sh before that... Ranting and raving about he spent all this money and it only went X months/years before
    via u/Zebov3
  • 26
    completely breaking down. One of my work buddies got it up on a lift and started looking it over. He opens the oil drain plug and NOTHING comes out. He pulls apart the engine and the oil could now be best described as glue. Owner talks to the guy and asks when the last time he changed the oil was. Guy had zero idea what he was
    via u/Zebov3
  • 27
    talking about - he had no idea that you had to do that. He assumed you just added gas and that's the only thing you needed to do. The engine was a complete loss, which meant the car was a complete loss to him.
    via u/Zebov3
  • 28
    [d... Not a mechanic, however I have story for this. Some years ago, here where I live there was a fairly widespread craze of mixing oil (I don't remember the type, but it wasn't at all related with the engine like sunflower oil or something like that) with diesel for better fuel consumption. The thought was that this type of oil would burn
    via u/[deleted]
  • 29
    anyway, and mixed with diesel it would give the same kilometers for less money. Of course it wasn't the brightest of ideas, so I remember that despite being fairly young, I remember strongly advising against this practice. My mother didn't listen to me, and proceeded to top her Mitsubishi Pajero Turbo (great car for fuel economy, I
    via u/[deleted]
  • 30
    know) with whatever oil she used. Now, to be fair the car held up pretty well despite the ab e, wich it's because it was a tank, however it eventually succumbed. If I remember correctly the fuel pump completely failed and had to be replaced entirely, but I might be forgetting stuff. The funny thing is though that the mechanic,
    via u/[deleted]
  • 31
    after looking at the engine for about 3 minutes or something like that, asked almost angrily to my mother if she was using the oil. When questioned how he knew that he said something along the line of: "its the fourth this week that comes in with this issue".
    via u/[deleted]
  • 32
    Goyteamsix I had a guy bring his motor swapped late 80s F150 in for some transmission work. These came factory with either a 300 straight six, 351 V8, or 460 V8. He put 2.31 carbureted 4 cylinder out of an old Ranger in it. The reasoning behind the swap was that it'd improve fuel mileage at the cost of some
    via u/Goyteamsix
  • 33
    speed. The thing could barely move under its own power. If you floored it, it would top out at about 55mph, wide open, and take a good minute or two to get there.
    via u/Goyteamsix
  • 34
    Fu... Not a car mechanic, but I knew a guy who used self tapping screws to fasten a roof rack to his car. Edit: A few people have asked if it worked. Yes, but it leaked. I would not recommend it though, because the roof sheet metal probably doesn't have. much load bearing integrity.
    via u/Fusiontechnition
  • 35
    Cheezburger Image 10487382272
    via Getty Images on Unsplash+

    The image does not depict the actual subjects of the story. Subjects are models.

  • 36
    Gr... Not a mechanic, but a car enthusiast. Saw a couple of cars, where owners didn't know what basic maintenance was. Like no oil change, no break pad change. The oil turned into jelly and you had to scrape it out.
    via u/Gregorinio
  • 37
    The most ridiculous thing were the brakes. My mechanic friend showed me the brakes of an elderly ladies car. The brake discs were gone, like almost completely wiped down to like 5-6 mm. She said to him "the car feels weird, while I brake".
    via u/Gregorinio
  • 38
    31nigrhcdrh Lady stated that her car said low coolant, so she filled up the coolant. She made it about a mile and the car started running terrible and cut off, shop rollback picked it up. She filled up the coolant by removing the oil cap and topping the motor off with water
    via u/31nigrhcdrh
  • 39
    [d... Let me tell you about diamond plate guy and Focus bro. Diamond plate guy had two things he used to modify his truck: A drill and a ton of diamond plate. It was an absolute base model V6 Ram 1500 with the exhaust chopped off, which I thought was bad enough until I opened the hood. He had drilled or glued diamond plate to EVERY flat surface.
    via u/[deleted]
  • 40
    Air filter box, Intake manifold, fan shroud, etc. This was 18 months ago. My eyes still haven't recovered, but this isn't the end. He had some crappy wheels that he had painted white himself. I know this because he painted the inside of the wheel where it seats to the hub, which caused them to seize to said hubs. I literally had to buy a bigger hammer to smack them off.
    via u/[deleted]
  • 41
    Focus bro: Guy had a custom straight pipe, full Sparco race seats, five point racing harnesses, lowering springs, and...a base model, automatic Ford Focus SE.
    via u/[deleted]
  • 42
    [d... Not a mechanic, but while sitting in the shop waiting for my own car to have work completed I witnessed a customer and their mechanic talking about the customers car needing suspension repair. The customer had tried (unsuccessfully) to do the repair himself. The mechanic
    via u/[deleted]
  • 43
    asked him why some lug nuts were missing and others were loose. The customer replied how he thought he would be helping the mechanic by "loosening the tire" for him. The customer had driven 20 minutes to get to the shop with a tire held on by a few loose lug nuts.
    via u/[deleted]
  • 44
    Clintman Dudes spending thousands of dollars modifying their pickups for offroading, even though they spend 99.99% of the time on highways and the furthest off of a road they ever get is a logging road that a stock Forester could tackle with no problems. And then complain about extra- fuel mileage, and "having" to pay for new 35 inch
    via u/Clintman
  • 45
    knobby tires that only last 10k miles because they wear out super quickly if you drive mostly on pavement, and having to replace their front wheel bearings every other year because those larger wheels and tires are a lot heavier than the stock ones,
    via u/Clintman
  • 46
    and being super surprised to learn that parts for a 3/4 ton pickup can cost multiple times more than the comparable ones for the small sedan they sold to afford their bro-truck.
    via u/Clintman

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