What weight oil in a cat 3406 engine?

The recommended oil weight for a Cat 3406 engine is typically 15W-40, which is suitable for a wide range of temperatures and provides good protection against wear and deposits. In colder climates, a 10W-30 or 5W-40 may also be used to ensure better cold-start performance. Always refer to the engine's service manual for specific recommendations based on operating conditions.