What is typically made of metal and may last the lifetime of the engine?

The timing chain is a crucial component of an internal combustion engine, specifically designed to synchronize the rotation of the crankshaft and camshaft(s). Unlike a timing belt, which is typically made of rubber and may require replacement around every 60,000 to 100,000 miles, the timing chain is made of metal, often steel. This metal construction provides significant durability and strength, enabling it to withstand the rigors of engine operation over time.

Since the timing chain is built to last, it is often designed to endure the lifetime of the engine under normal operating conditions. Unlike the other components listed, which are subject to wear and require periodic replacement, a well-maintained timing chain can function efficiently without needing replacement unless there is a catastrophic failure due to lack of maintenance or other issues. This longevity makes it a distinctive part among the options presented.