[Guy]

Changed the oil today in the 8V92, something I have done several times, and something I have had done in shops before . When I removed the plug, I was surprised at how easy the plug came out. Never been a " gorilla tight " plug, but I don't remember it being so easy. It is a plug, not a bolt, so there is no sholder to make positive contact with the pan. I have experienced no drips or leaks, so I don't know if I am just being overly cautious. Before putting the plug back in, I examined the threads, and they look fine , both the pan and the plug. I would estimate that I am able to get about 10 ft lbs on the plug. Any more than that it continues to move. I cheaped out years ago and my Harbor Freight torque wrenches, both inch lbs and ft lbs are worthless at low values. I have not replaced the oil in the engine yet, being on the fence regarding this plug, which has served me well for 40 thousand miles and 8 oil changes. Any thoughts?

I can't believe after 50 years of working on cars, I am having an issue with such a simple thing......

[Richard]

I would be prepared with a heli coil when i pulled that plug

[HoosierDaddy]

So is it a tapered “pipe” thread?

[Guy]

My current concern is the plug coming out on the road  and giving me the need for an engine overhaul. I will compare it to electrical and plumbing plugs to see if it is tapered. I don't think it is. This is the same plug that has always been in the motor since we purchased it 4 years ago. All threads look good. What has changed ? It looks just like a pipe plug that has a recess in it for a 3/8 dirve ratchet extension.

[folivier]

Is it possible there is an o-ring or gasket that fell out?
Can you post a picture of the plug?

[MrE]

I would get an oversize drain plug. https://www.amazon.com/Oversized-Oil-Dra...Drain+Plug

[Guy]

It appears that it is a 1/2-14 npt pipe plug. Since it is just a plug, there is no way to use a washer. If I tried, I think I could continue tightening it until he goes completely in the oil pan. Thant would make my day. It has a recess on  the end of it  it to accept 3/8 inch ratchet and extension to tighten with . I thought it was something special ! Tomorrow I will go get a standard 1/2-14 oil drain plug that has a with a washer and a shoulder for the washer. Maybe when this engine was overhauled in 2013 they lost the original plug, and decided and electrical type cap  plug would do the job?  If you GOOGLE 1/2 npt cap plug, that's what I have.

[Tf175]

My 8v92 has a flanged drain bolt /plug with regular hex bolt head for wrench  don't know exact size , thinking it's 5/8 or 3/4 straight threads , not pipe . Detroit manual calls for 24 to 35 lb-ft torque , but no size or type of plug is given . Those figures sound like a flanged plug .
I would look for a longer plug , I think the male square drive plug may have more threads than the female drive .
NPTF fittings exist , specifically for fuel applications,  perhaps that would tighten better ?
Mil spec Teflon tape is thicker than normal tape , if wrapped on threads that don't protrude into the pan " proper " there would be no contamination. 
I tend to fuss over such things that can cause a catastrophe as well .

[Guy]

Mystery solved. I was not dealing with clean threads in the oil pan, but the drain plug threads were clean. I believe the shop that changed my rear air bags last year, and also did an oil change, was not comfortable with the drain plug, and used some type of black Permatex type of material on the threads that has held in there for 6000 miles. After removing this goo, the plug now bottoms out and feels like it used to. I will monitor the plug, but though I have never been a fan of it, I have never had a drop of oil leak on the pan. Here are a few pictures of the plug. I am thinking that someone must have given it a few ugga duggas in the past, or is that not a 3/8 drive plug ?

Has anyone installed a Fumoto valve on their oil pan? 

Thank you all for your advice. It is much appreciated.            

[Tf175]

Yes,  3/8 square drive plug . I checked parts manual , your engine likely came with that 1/2 npt plug . Detroit used several drain plug sizes for various engine types.
Glad you worked it out !