How to Replace an Engine Main Oil Seal (Quick Guide): The main oil seal (rear main seal) prevents engine oil from leaking where the crankshaft exits the engine. Replacing it involves removing the transmission, flywheel or flexplate, then pulling the old seal and pressing in a new one. It’s a labor-intensive job but crucial for preventing oil loss and engine damage. Always torque bolts to spec and check for leaks after reassembly. #CarTips #DIYMechanic #MazdaRepair #RearMainSeal #EngineMaintenanc