Replacing the rod bearings on the S85 engine in the E60 M5 and E63 M6 is a crucial preventative maintenance step due to the engine’s known susceptibility to bearing wear. The high-performance V10 engine is prone to rod bearing degradation over time, especially in cars that see frequent high-revving or aggressive driving. Worn bearings can lead to a drop in oil pressure, increased friction, and eventual bearing failure, which could cause catastrophic damage to the crankshaft, connecting rods, and other internal components. Since the S85 engine is complex and expensive to repair, replacing the rod bearings at recommended intervals (typically around 60,000 miles or sooner depending on usage) helps mitigate the risk of major engine failure, improves oil flow, and ensures smoother engine performance. Addressing this issue proactively can prevent costly engine rebuilds and help preserve the longevity and reliability of the M5 or M6, making it a wise investment for maintaining the health and performance of this high-revving, naturally aspirated engine.