Why is the idle engine sound loud in a new car?
2 Answers
The reasons for a loud idle engine sound in a new car are as follows: Higher idle speed setting: During the break-in period of a new car, manufacturers set the engine idle speed higher, which naturally results in a louder sound. After the break-in period and the first maintenance, the idle speed will decrease, and the sound will also reduce accordingly. Break-in noise of components: When a newly assembled machine is used for a certain period, the friction plates will experience some degree of wear. The lubricating oil then carries away the metal particles worn off. This process can produce a louder sound. Once the machining marks on the friction surfaces are smoothed out and the components fit more closely, the engine sound will naturally decrease.
I just bought a new car recently and noticed that the engine noise at idle is surprisingly loud, which makes me a bit nervous. This is actually quite common, especially during the first few thousand kilometers of the break-in period for a new car. All the engine components are freshly assembled, and the friction during the break-in process is higher, just like new tires need a few days to fully settle in, so the operating noise naturally tends to be louder. Additionally, if it's a direct-injection or turbocharged engine design, they optimize the air-fuel ratio at idle to save fuel, which inherently makes them noisier than regular engines. I've also noticed a significant difference between using 92-octane and 95-octane fuel; lower-octane fuel burns less efficiently, resulting in a rougher sound. When the weather is cold, the higher viscosity of the engine oil makes piston movement more strenuous, amplifying the noise even more. Don’t worry too much—it usually quiets down after a month or so of driving. However, if the noise is accompanied by severe vibrations or sounds like metal clashing, it’s advisable to visit the dealership to check the oil pressure and exhaust system, just to ensure everything is okay. Safety first, after all.
