I think that depression/reservoir in the rubber coupler is designed to catch the oil. I cleaned mine at 70k or so and it had no more oil than that in it. It would make sense to induce a small amount of oil into the conbustion chamber that way from an emission standpoint. My throttle plate was pretty clean also with that mileage.jrmarshall01 said:Is oil sludge more of a problem for engine performance than carbon deposits? How worried should we Enclave owners with DI engines be about this? If this is a worrisome issue, installing a pcv oil mist can sounds beyond most owners capabilities...and does it require frequent maintenance on its own?