1685248 Seal-Isolation Fits Caterpillar ModelsOne New Aftermarket Replacement Oil Pan Isolation Seal for Caterpillar (Cat) 3406E, C15, C16, and C18 Diesel Engines This aftermarket replacement oil pan isolation seal (also referred to as an oil pan gasket) seals the joint between the engine block and the oil pan on Caterpillar heavy duty diesel engines. The seal provides a cushioned, vibration dampening barrier between the oil pan and the engine block, preventing oil leaks and protecting the engine