Does anyone have a RX 350 Lexus that makes a rattling noise while driving down the highway. It sounds like it is coming from the overhead luggage rack. I have complained to the dealer to no avail.
Make sure the knobs that secure the roof rack crossrails are tight. A loose one on my 2000 Blazer was a cause of a rattle.
Might it also be something loose in the sunroof? Try opening it a little, see if the rattle changes.
If you’re no using the overhead luggage rack, remove all the cross bars, they (slightly) reduce fuel economy.