Chaps

Hi, just picked up my accord tourer 2.2 diesel 2015 last week. Theres a slight whining noise from the engine, similat I guess to a quiet super charger kind of noise. Seems to dissappear above 2000rpm or you just can't hear it then. Engine pulls well, only averaging around 40mpg, was hoping for more but may be the norm? I've had a mechanic had a quick listen and seems to think its just abit of impeller noise from the turbo and nothing to worry about. There's quite abit of chat on the Internet about the engine being abit noisy and may be the norm. Is it worth booking it in Honda for them to take a look. Cheers all