Seafoam is a highly acidic compound and your not supposed to leave it running through the motor for more than 2 miles. I did it to my car and it idled really weird and had no power until I changed out my oil. When I was draining it, it was nice, black, and had a ton of junks of sludge. Now the car runs great. Even if your oil is still golden, doesn't mean it's not dirty. There could be other parts of the motor storing dirty oil such as the oil pan. I would rather change it clean knowing my car is still running great than change it when it's dirty and sludge has begun to build up. If your running dyno oil, you can change your oil every 3-4k. If your running a full synthetic, I would recommend every 5-6k.