My 2015 Isuzu MU-X makes an annoying high-pitched whistling sound when driving at high speeds. Doesn’t do it as much below 80 km/h, varies in volume, worse when trucks pass in the other direction. Is it a door seal, or an under-greased wheel thingy, or something else?
It could be some form of wind noise, either from the door seal, the rear view mirror, windscreen trim, or anything else that might be in the wind stream. To check the door seal, try running a strip of tape around it to block off the door gap and see what that does. It’s going to be a process of elimination.