Ahh. Engine sludge. My truck had not so much, as its engine was rebuilt just 20 or so years ago. But my car!!!! It has no filter, engine never out, pan never off. It had more than a full quart of sediment in the pan, and the special pontiac sedimenter. There was just over an inch in the whole lower part of the pan.
As long as it's in there, and not disturbed, it doesn't do any harm. But if it gets back into circulation, its not ideal. My car was, and is, still on the road. It does now, take about a quart more oil at oil changes. The lower than spec'd volume was what eventually prompted me to clean it out, that, and the fact that the new oil instantly turned black. Well, it did take two minutes of running.
