Folks in cars, I feel I need to say this again, just because it happened again this morning.
When you shout something out the window at a cyclist, regardless of whether it's friendly advice, outright harassment, or "hey, didn't we meet at that vernissage last week?" you need to know one thing.
We can't hear you.
Whatever it is you said, it sounds like this:
We just can't hear you. Even if you were going to say something helpful or informative. So don't bother.