We don’t know that the OP has an Impala. The OP has never said or implied what he has.
Opps sorry it’s a 2003 Kampala
The “K” is just below the “I” on the keyboard. The OP is a regular here with three different names, you may remember the lower control arms and brake parts purchased and brought to the repair shop for installation.
But the “a”, the second letter in the name, is way on the other end.
I’m still confused as to what the car is.
“If I was a betting man (which I’m not), I would wager that the source of the problem is the result of not using a new crush washer on the drain plug after each oil change.”
"The rubber seal on the OP’s Impala doesn’t require replacement during each oil change… "
We don’t know for sure that this car is an Impala ( “Opps sorry it’s a 2003 Kampala” ), but since I’ve still got 2 of them from different generations, I will verify that the plugs have rubber seals (that fill a recess to avoid over squeezing) and have no replacement crush washers.
I have never over-tightened an Impala plug, never stripped one, nor have I had one leak.
Also, I’ve never had need to replace a plug in hundreds of thousands of miles. It’s a good set-up.
CSA
For what it’s worth, I’ve seen a number of drain plugs tightened to the point they would not budge even with heat, an impact, air chisel, or 5 foot cheater bar.
This problem was especially applicable to Subaru drain plugs that had been installed sans drain plug gasket.
I’ve never had to replace a plug either. I figure I probably changed the oil about 113 times in my '89 Toyota pickup (every 3,000 miles for 338,000 miles total).
The pickup, and some of my other vehicles, used crush washers, and I always kept a supply of nylon washers in my oil change kit. If there was any sign of splitting or deformation that gave me any doubt, I simply tossed the old one and put a new one on.
I have seen those GM plugs repeatedly overtightened, to the point that the captive seal was flat and allowed some seepage.
I agree it is a good design
On my personal Toyotas, I always replace the nylon washer. They get quite deformed, and I’m not sure I’d trust them a 2nd time
On Benzes with the copper washers, I’ve seen seepage when the washers weren’t replaced. But it was usually possible to get away with reuse
Same thing with the Hondas and the aluminum washers
Bottom line, you usually get away with reuse, but there’s always that one time, and that one guy
“I have seen those GM plugs repeatedly overtightened, to the point that the captive seal was flat and allowed some seepage.
I agree it is a good design”
No disrespect meant, but those two statements seem inconsistent to me.
mountainbike
Let me explain
It is a good design, because a non-hamfisted guy can tighten the plug correctly, and the next guy can reuse the drain plug
but if you’re a hamfisted guy, even the best designed part will fail, if you get your hands on it
And since most mechanics aren’t ham-fisted, the drain plug can be reused the vast majority of the time
a lugbolt could last 20 years with perfect threads . . . and then some idiot decides to drown the threads in antiseize, and the threads get bottlenecked, when he tries to torque it
Does that mean the lugbolt is a bad design?
Or does it mean the guy is an idiot?
Yeah, but that’s also true of every drain plug I’ve ever pulled.
Hah! - Kampala - The capitol of Uganda!
OP must be a real big shot if he drives the capitol of a country.
It is 2003 impala LS with about 114000 miles on it
It is 2003 impala LS with about 114000 miles on it
Thanks. 
My Impala LS 3.8L From That Generation Has A Steel Pan. I Suppose Somebody Could Cross-Thread And Seize A Plug Into It If They Were Stronger In The Arms Than They Are In The Head. I’ve Never Looked A 3.4L Pan, Though.
The car is 13 model-years old. I’d be tempted to drill through the drain plug, thread it, and put a smaller plug in there.
@brm7675Is it a 3.8L (3800) engine?
CSA
Repair kits that self-tap into the original hole and have a smaller drain plug screwed into the center are readily available already.
"Repair kits that self-tap into the original hole and have a smaller drain plug screwed into the center are readily available already. "
Of course. When I re-read the original question I discovered that the plug could probably be removed. For some reason I was thinking it would not come out, again.
CSA
I see you point.
Were the original plug stuck in there for all time, your idea would be one I’d support.
@brm7675, if you drive back to the previous shop to have them do the oil change, bring your own torque wrench and demand that they allow you to observe the drain bolt being torqued in correctly. Otherwise you will have this problem the next time you need an oil change because they will just over tighten it again.