A long time ago, a car maker made an engine, and it was a good little engine. It was designed for transverse applications, but it was so good, they put it in a longitudinal applications, too. That required some massaging of the oil pan, and it lost about 20% of its oil capacity.
The good little engine came with a requirement to use synthetic oil because it was equipped with a very good little turbocharger, which got very hot. It was very important to use an oil that could handle the heat, especially because there was less oil that there was originally intended to be, and it was before coolant afterrun pumps were really a thing.
The American dealer network wasn’t too keen on the cost of synthetic oil, so they put petroleum-based oils (dino) into the good little engines during routine maintenance. A lot of good little engines were run very enthusiastically by their owners and put out a lot of heat. The good little engines did not have coolant afterrun pumps, so the very good little turbochargers cooked that oil and made coffee grounds out of it when the engines were shut down hot. The coffee grounds moved into the oil pan on startup and plugged up the oil pickups which starved the bearings and lot of owners became big mad.
Some lawyers also became big mad and made a class action lawsuit of out it. But it was really hard to argue about because the coffee grounds didn’t fit the normal ways engines failed. There was no sludge.
So the lawyers asked around and finally it all ended up in my lap and I got to explain to the world about the difference between thermal oxidative stress that leads to sludging, and thermal stress in the absence of oxygen that leads to coking. And coking is what makes little coffee grounds that clog up oil pickups. And when confronted with that fact, the car maker folded and granted relief to a lot of owners who were big mad and a really really long warranty extension to any owner that had ever had an oil change at a dealership and had the papers to prove it.
The same car maker had a Head of Internal Combustion Technology who tried to tell me to my face that they did not have PCV issues. I was big mad about something else he had said in that meeting, so I offered to bring my intercooler (from one of his engines) in and turn it out on his desk. In front of his team. Somehow, I did not get fired for that.