Several things could cause this:
* Head gasket failure: This is the most common culprit. A blown head gasket allows coolant to leak into the engine's cylinders, and subsequently into the oil pan, contaminating the oil.
* Cracked engine block or cylinder head: Similar to a head gasket failure, cracks allow coolant to mix with the oil.
* Coolant leak into the oil passageways: A leak somewhere in the cooling system could introduce coolant directly into the oil passages.
* Condensation: While less likely to create significant yellow sludge, excessive condensation in a rarely-driven vehicle *could* contribute, especially in humid climates. However, the amount of water needed to cause noticeable yellow sludge usually points to a more serious internal leak.
This is a serious problem that requires immediate attention. Continuing to drive the vehicle with water in the oil will cause severe engine damage, potentially leading to a costly repair or even engine failure. You should have your Dakota inspected by a qualified mechanic as soon as possible to determine the source of the leak and have it repaired. Driving it while the oil is contaminated will only worsen the damage.
