Turbo seals are designed to keep pressure, dirt and debris out more so than to keep oil in. Turbos are not designed to see oil pressure at the rings. The seals do keep oil in by default at times as some oil will find its way to them. Turbocharger failure is usually the symptom of another issue. Misdiagnosis, incorrect sizing, installation errors, oil starvation/contamination, etc.. are all a much larger cause of "failure" than defects. Sometimes there is a common pattern with certain models that cause people to see them as defective and sometimes they are but often times it is abuse.
The S369 is a perfect example. The airflow claims support the theory that everybody with an S475 should swap to the S369. It spools better, its generally less expensive, and supposedly flow better. Why not? People are seeing why not. You cannot expect an S300 frame to support 800+ HP reliably by itself. Airflow on the compressor side is only a small percentage of the equation.
When we see one pushing oil it is usually:
drain blockage
excessive crank case pressure
just plain wore out across the board
Excessive bearing clearance (improper bearings or wore out)
Excessive "in and out" ie. thrust failure. wiping out the seals entirely
Oil level too full (yes. That exists. The drains can be extremely close to the oil level in the pan at times.
Overspeed does tend to cause leakage but usually when we have one that was clearly overspeeding it shows signs of doing it for quite a long time. It had been abused since day one causing the rest of the turbocharger to wear exponentially ultimately causing the leak.
