Just got back from an oil change at the dealership. During our convo, I asked about severe service intervals. They didn't know of any on our 3.5 liter v6 which is MPI as far as I know. They also said that the GDI engines are having issues when going beyond the recommended oci. They are hard on oil apparently and it has lead to sludge and engine death if not changed. An example at 10k came up in the course of convo. I assume that meant multiple changes at 10k but who knows. Bottom line is they said the engines dirty the oil and are hard on it so stick to the intervals or shorter. Just an FYI based on what they said