on the exhaust side you have the air being pushed out...through the exhaust...on the intake side the air iscoming in. seems to me any oil that go pushed past the seal would just be vaporized and sucked back into the turbo charger and forced out, and back into the engine. i believe this was happening on my stock turbos due to whenever i boosted enough to trigger my blow off valve, i would have a strong smell of burnt oil.