I changed the oil in my Dakota today. Exactly 2900 miles since the last time about 2 months ago. I've done mostly just highway driving and a little around town. When I took the oil cap off I noticed a little bit of yellow sludge where the funnel goes. Just a little bit. It wiped clean with a towel. The oil that came out of the drain was perfect. I've never seen this before. I have 118K on my truck. Anybody see this before?