What's the priciest repair you've had to make as a result of car owners neglecting basic maintenance?

Curious to hear from mechanics about the worst situations you’ve seen/most expensive repairs you’ve had to make as a result of car owners neglecting basic maintenance (oil changes, brake checks, tires, scheduled maintenance, etc.).

Specifically, I want to know:
What was the major repair that needed to be made as a result of neglecting something more minor?
What was the price tag on that repair?
What more basic repair/maintenance service could have prevented it?

Ps. This is for an article I’m writing and I’d be happy to link back to your shop/website if we use your tip. Thanks!

Not for me, since I work at an auto repair shop.

One of our fleet customers brought in a 3 year old Dodge Ram Promaster delivery van with a complaint of ticking or clattering noise. The mechanic I assigned the job to diagnosed a couple of noisy valve lifters, recommended replacing all the lifters. I informed him that this truck had gone 85,000 miles (from new) before having its first oil change, and that when the oil was drained out it was so sludged up that it wouldn’t pour out of a coffee cup.

Also the sludged oil may have caused a broken flex plate.

We recommended no repairs to the engine at that time, we advised the customer to drive it until the noise got worse or started causing misfires and then to replace the engine.

So instead of spending a few hundred dollars on oil changes over 3 years, the customer will end up needing a $8,000 engine.

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:open_mouth: That one’s going to be hard to beat…

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As a mechanic, this would not apply to me as I take care of my vehicles.

Worst case scenario is a trashed engine due to lack of oil changes or not checking the oil level on a regular basis. This runs into the thousands of dollars. I’ve seen quite a bit of this.

Some may remember the poster on this forum about 10 years (?) ago who was about to move to CT from CA. Her hubby bought a brand new Ford diesel pickup and decided to mod it for extra power for pulling a travel trailer.
On the uphill climb to Flagstaff, AZ the engine blew up because of that modification and they were distraught since warranty would not (and rightfully so) cover the repairs.
That modification cost them 13 grand out of pocket.

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I once overhauled a Ford LTD engine and the owner called me a year later complaining of an oil leak. The owner dropped by and left the car for inspection and I found that there was no leak and the oil had been changed very recently but the engine was knocking and the car had 14K+ miles since delivered. When the customer was given the news that another complete rebuild was necessary with no warranty the conversation got hostile despite the admission that the hood had not been opened since the overhaul until the knocking was heard resulting in a visit to a quick change shop that the car ‘must have a leak since the oil pan was empty.’ That was many years ago but today such a situation would cost well over $5,000 these days.

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I think about that post every time I see a new question on here about programming or “chipping” a car.

That Ford diesel story should be mandatory reading for anyone wanting to “reprogram” their car. Ford engineers know far more than anyone else on how your car should run. Leave it alone, I say.


I used to work in a 4 wheeler shop during the summer. One day a young man brought in an ATV, newer model, that wouldn’t start. When the mechanics got into the engine, they found the inside of the cylinder was full of mud. Turns out the young man had been “mudding” with the ATV, and managed to suck mud up into the air intake. So that repair was a couple thousand dollars, as I recall.

About a month later, the young man brought the ATV back…with the exact same issue. Apparently his wealthy father wrote the check for the first repair, and was going to cover this second repair bill too. Unbelievable, but it happened.

I imagine there are a few incidences of cars getting totaled in an accident due to neglected brakes or tires.

If the warranty is voided, then replacing the engine becomes an un-economical repair, since there would presumably be no warranty going forward. That’s a lot of money to spend on a repair that has no warranty.

Not a pro mechanic myself, but what we are hearing here is the maintenance intervals recommended by the new car manufactures of late seem to have lengthened, longer time between needed services, some say b/c they are trying to make the “cost to own” stat look better to car buyers. That, combined w/engines seeming to use oil at a quicker rate (likely b/c trying to post better mpg stats), seems to be causing quite a few new engines being installed than some years before.

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Why would you think that? The replacement engine comes withn a warranty…as long as the tune is returned to the factory calibration.


The single biggest repair cost in most vehicles would be an engine replacement. The biggest neglect people do is not to check the oil level regularly. The oil level gets low, the engine is destroyed and Surprise! The owner gets a large bill.

There are many posts on this site of exactly this situation… whether the poster admits it or not…


The biggest repairs that I’ve personally had to pay for have been transmission overhauls. All on a Dodge truck that had the fluid and filter changed every 30k miles. I’m actually a little less faithful in changing it on my vehicles now. It didn’t seem to help on the one that I really tried to maintain!

I still try to change it every 50k or so.

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I have not experienced that. My truck, after 70,000 miles has only required one pint total, and that was after using compression braking in the mountain. 5W-20 oil. Get oil&filter at ~20% oil life remaining.

About 10 years ago the service manager at a Ford dealer here was telling me about a guy who bought a top of the line Ford pickup with every bell and whistle available. It was somewhere in the neighborhood of 50 to 60 grand.

He brought it in at 3k miles for the first oil change. The next trip in was on the back of a tow truck with a wiped engine at 20-25k miles.
After that first oil change at 3k miles the oil was never changed again nor was the hood ever raised to check the oil level. And per the usual, the truck owner blamed FOMOCO for it all…

Very sad that someone would shell out that kind of money and then ignore the life blood that keeps it going.

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Engine problems on newer cars of course vary by make/model/year.