Why is the BMW X5 engine so loud?

[LeBrantley]

It could be caused by reasons such as engine oil issues, increased carbon deposits, aging engine mounts, or deteriorated soundproofing rubber strips. Proper maintenance can help reduce the degree of engine noise increase. 1. Engine Oil Issues Engine oil can indeed cause differences in engine sound during operation. Some owners notice that the car sounds louder after the first maintenance. This is because new cars come with factory-installed initial engine oil, which differs from commercially available engine oil. Initial engine oil is formulated to suit new engines where components haven't fully broken in due to manufacturing tolerances and processes, resulting in higher internal friction. Thus, initial oil has lower viscosity and better heat dissipation but lower requirements for cleaning and anti-oxidation (rust prevention). Some initial oils even contain grinding agents to accelerate the break-in of friction components. Replacing this initial oil during the first maintenance with higher viscosity and different formulations can indeed make the engine sound louder. 2. Increased Carbon Deposits Carbon buildup is unavoidable in cars. Over time, severe carbon deposits can lead to reduced engine power, increased fuel consumption, and louder noise. During operation, impurities in gasoline can form carbon deposits under high temperature and pressure. Even high-quality gasoline contains long-chain hydrocarbons that burn slowly and incompletely, contributing to carbon deposits. The best we can do is adopt good driving habits and timely maintenance to minimize carbon buildup. Poor maintenance or driving habits can lead to severe carbon deposits over time. 3. Aging Engine Mounts Faulty engine mounts can also cause increased noise, along with additional vibrations and resonance. The engine is secured in the engine bay by several mounts designed to absorb vibrations. These mounts have rubber cushions to dampen vibrations and prevent them from transferring to the car body, which could cause unwanted resonance and noise. 4. Deteriorated Soundproofing Rubber Strips Even with proper engine oil maintenance, cars may sound louder inside over time, primarily due to degraded overall soundproofing.