I just completed the cleaning phase using Auto RX on a 1992 Buick 3.3 V6. The oil appeared to be very clean, similar to when I put it in 1,500 miles ago. The oil filter seemed to be noticably heavier, I'm hoping that's because it's full of stuff I don't want in the engine. When I emptied the oil collection pan at the bottom I could see the dark black color of the Auto Rx mixed in with the oil. During the rinse phase will the oil likely be darker?