Oil plug fell out; engine shot; servicer won't accept blame!

The drain plug should not fall out in a day, week, month, decade or millenium. Sheer common sense says it’s in there for the duration until the next service unless someone ham-fisted jackass botched the oil change.

Are millions of customers supposed to be responsible for constant checking of the drain plugs? Not iMO.

If one calls an electrician out who botches an electrical repair which in turn burns the house down is it the responsibility of the homeowner to double-check their work? Again, no IMO,

Personally, I don’t think there’s any way the dealer wins this in small claims court unless the judge and dealer share the same tee times…


I don’t necessarily disagree that the plug should be in there for the duration, but without the information on the condition of the pan threads, I just don’t see that there can be a direct link back to the dealer. How would the dealer determine after four months that no one else had the car up on the lift and messed with it, or (not saying this happened at all but) that someone else caused vandalism to the car, or the owner themselves? Just saying unless there is damage to the pan threads, after four months time and no indication of seepage during that time, it is hard to actually envision the dealer being on the hook. The OP has been silent on the condition of the threads and possibly a leak that had been going on for months. Regular checking of the oil would have indicated a loss of oil before it was catastrophic even if the plug was loose all the time. I just think that the owner has the requirement to mitigate their loss as in anything, and letting it go until the plug actually came out would be irresponsible. True it is unreasonable to expect someone to crawl under the car and check if the plug is tight, but it is not unreasonable to check the oil every couple of weeks or so. I gotta believe there was some oil loss way before the thing actually fell out.

I tend to agree though, the engine may not be shot so put a new plug on (if the threads aren’t shot) and try it out.

Yes, I think it is down to a time limit

  • BUT -

This is about the likelihood of the dealership being responsible. It’s not a black and white issue. The longer that time frame, the more likely the drain plug falling out was caused by something else - and for the purposes of defending oneself in court, what caused the drain plug to fall out doesn’t need to be identified.

And we don’t know that no one else touched the car (or at least for the purposes of making a judgement, we recognize that the plaintiff has a vested interest in saying that.) While I am sympathetic to the OP’s plight, I’m trying to point out where I think this is leading.

My point about the plug being in there for the duration is that a properly tightened drain plug screwed into good threads is NEVER going to come loose even in a 100 years of driving unless someone removes it.

It’s no different than the notion that cylinder head bolts will come loose.

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Didn’t this start with the claim that the shop that changed the oil is the one that has done this and other work for the owner, and that the owner of the car has receipts over the years to show that. It’s pretty much impossible to prove that the owner didn’t go anywhere else, but the stack of receipts should show that the services that were done were all the regular services. So it wouldn’t be completely ridiculous to believe the owner’s claim that no one else has touched it in the mean time.

Drain plugs do wear out over time, and they do require replacement from time to time, but the only person who would know when replacement was needed is the person who changed the oil. That’s the dealer. That’s also the only person who would know how tightly the plug was put in, what procedure they used to ensure proper torque, whether the oil plug was over tightened and stripped and replaced, etc.

My guess is judgment for the car owner - replace engine with equivalent.

I disagree.
Oil drain plugs are bathed in oil every time they’re removed, as are the threads that they mate with. And they’re reinstalled still wet with the oil. Properly installed and torqued, a drain plug does not wear out. The problem I believe is lack of attention to proper installation resulting in thread damage or overtorquing, perhaps repeatedly… I believe the latter to be the most common.

It could be argued that the plugs’ well-oiled surface combined with the well-oiled drain hole threads are contributors to the overtorquing, but I would argue that a competent mechanic should understand the conditions and compensate for them… and not overtorque the plug.

My '89 Toyota pickup reached 338,000 miles before getting totaled by an errant Hyundai. I figure I changed the oil on that one over 100 times. The threads never wore out. I’ve had similar history with all my vehicles for over 50 years. Never a damaged or worn out thread.

In summary, I contend that drain plug or hole threads do not wear out. Any and all thread failures are operator error. I further contend that any shop that says the threads wore out is either full of BS or unable to properly change oil.

That’s my story and I’m stickin’ to it! :grin:


I’ll admit I never wore a drain plug out or stripped the threads but I don’t let anyone else change my oil. Never the less, I still think 4 months to hold someone accountable is toooooo long, and the other issues like when the oil was checked are yet to be answered.

In small claims though, where there is doubt on both sides, the judge may well just split it 50/50, providing they can find another engine with 100K on it to swap like for like. I can imagine if this happens much that it will be the end of $20 oil changes if there is no limit to liability.

This drain plug with a built in o-ring seal can wear out. The o-ring can fail and that would allow it to loosen. Also, the shop could have stripped out the old plug and replaced it with some sort of temporary rubber plug or an insert. We don’t know that, do we, unless there’s some sort of note on the receipt or the shop record.

Other than an impact, what could explain a well and properly tightened oil pan drain plug falling out after 4 months? How can this set of facts happen? Examining the oil pan should tell us if there’s been an impact.

It can allow it to seep oil past the seal but a properly tightened bolt like that is not relying on o ring compression to hold it in. The groove is designed to provide about worst case 80% compression of the seal before it bottoms out on the torque limit feature of the plug. The friction on the threads and bolt head hold it in.

Simple. It wasn’t properly installed and/or tightened.
It could be an accumulation of overtorquing, distending the threads until they finally failed, or a single overtightening on the last oil change that left the threads barely hanging on. It could also be that the threads were cross-threaded at some point, leaving them weakened. Or the plug could simply have been left untightened.

If the plug had always been well and properly tightened, and the threads had not been physically damaged by bad installation at some point, the plug would not have fallen out.


That’s exactly my point. An owner, armed with a set of receipts for oil changes and services from a single shop over a multi year span, can make a pretty convincing argument that this situation would not have happened without some form of improper practice.

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In the worse case scenario, they or someone could drill out the hole, re-tap it, and install a slightly larger oil pan plug.

As a mechanic of 40ish years it would seem that me that I should have run into a worn out drain plug along the way but not so. How does one wear out oiled threads? I suppose if the plug was screwed in and out a few million times that could take a toll on it. That’s a lot of oil changes…

The drain plugs on my antique Harleys (68 years old and 74 years old respectively) should have been worn down to the nub decades ago with this logic…

Mountainbike is dead on correct. Those guys likely snugged it up and a combination of thermal changes and vibration eventually bumped it out of its hole.

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To EVERYONE who has been following or responded to this thread after I posted,I would like to say “Thank You”! Based on all the information gleaned from comments plus some plain old-fashioned research, I again contacted GM who in turn discussed the matter with GM. The dealer agrees that we did absolutely nothing wrong or improper to encourage the plug to fail and there is a definite possibility that a service error may have played a role. Based on this, the dealer has agreed to fully cover the repair costs and reimburse any expenses we incurred. So… again… thanks all for your comments and opinions and we are glad we did not have to resort to legal means.

The car is being repaired (new engine) as I write.

Have a good day and motor on!!


Great news, John!

Although I’m sure you’re not thrilled with the loss of use of the vehicle, the anguish, and other problems associated with all of a sudden needing a new engine, this is no doubt the best outcome.

Also, hats off to the dealer and GM for owning this for a loyal customer.

Thanks for promptly reporting the news. Let us know how your machine purrrrs after the new power plant is in place.
CSA :palm_tree::sunglasses::palm_tree:

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We’ll, congratulations. And thanks for filling us in on the outcome. It’s always helpful to know how things work out.

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Fantastic! I’m thrilled at this resolution, and… can I count on you to help solve some issues of mine too?? :rofl:

Seriously, congratulations and sincere thanks for posting back. I’m absolutely thrilled for you.

Good for GM to deal with this problem in a professional and courteous manner. Wishing you all the best OP! Happy motoring.

the OP can change the thread title. maybe oil plug fell out, got new free motor

Well that’s good news and I’m happy to be wrong.