Holy crap, guys. Holy crap.
Car comes in today, the make and model of which I will not specify, but it was a smallish engine in a vehicle that sees mainly highway miles. In this case, roughly 15,000 of them since the last oil change, according to the lube sticker.
Oil light was flickering at idle when cold. Engine seemed to sound okay, so I carefully drove it around the block for a road test for other concerns. Oil light stopped flickering unless you bogged the engine down to <600rpm with the clutch. Could be bad pressure switch, engine sounds fine. Oil level is slightly overfull, and the oil on the dipstick is dark.
On the lift, vehicle has no oil leaks, including the oil pressure switch. (A failed switch usually leaks) It didn't click with me at that moment, but this also means that the car probably never needed to have oil added, either.
Pull the drain plug. Nothing comes out.
Nothing's coming out. The oil pan is vented to atmosphere, and the oil, which has been confirmed to exist, doesn't want to leave. It likes its home so much that it is completely ignoring gravity. Not only is the oil breaking the law of gravity, it is breaking the law of fluids, which is "Contained fluids want to be free."
I spin the oil filter off. No oil slurps out down the side of the block. The oil filter is a solid mass of jelly.
I stick a screwdriver in the drain plug hole. Come out, come out, wherever you are! I think to myself that this is like knifing a new bottle of ketchup, except clearly I was going to just be punching through a plug of sludge covering the drain hole.
Once again, I was failing to take into account other observations, namely the jellymould of a filter.
A little bit of ketchup-like black spooge glurps out, and then... nothing. I swirl the screwdriver around in there some more. A little more petroleum ketchup.
The engine had four quarts of frothy black ketchup in it, it had no liquid that you or I or anybody else would consider to be oil.
For about two hours, while working on other things, I would randomly walk by the car and perform my orbital lobotomy trick on the oil pan, and some more spooge would ooze out for a while, then just stop. There were no hard chunks. There were no liquidy bits. There were, thankfully, no shiny metallic particles. (The guy had just spent a ton of money on two of his other vehicles, and hey, we're human) There was only black ketchup, and somewhat thicker lumps of black ketchup.
This post is getting long, so I'll tell y'all how I corrected the issue in a subsequent post.
But for now... change your oil already! We don't say 3mo/3000mi because we like doing oil changes, we say it because healthy engines are happy engines and happy engines live a long time!