[fangbinwu]

Guys, I have a question about engine sound of my 06 325ci.
Normally it's running very well, the strange part is, when I drive highway for 30 minutes and I go to grocery for 10-15 minutes. I start engine again, the sound is different from my familiar sounds. it's more loud. However, if you let the engine rest for more than 15minuts after highway, the sounds are back to normal if you start again. 99% of the time when i am driving, the engine sound is very beautiful. I do not know what's going on with my engine or other parts.
if you guys have any thoughts, please share with me .
I do appreciate very much