A friend of mine had exactly the same problem. In some cars, when you look through the top of the front dashboard in certain light conditions, you see the leather shows this white-ish patina, as if left by the residue from the application of some leather conditioner or similar product. Fact is, no matter how hard he tried to clean it up, it comes back.
What he did was to apply thin, even coats of (black) shoe polish with a lint-free cloth, took him some time but the nero dash now looks pristine. TBH, he gambled on this. The side effect (nothing is perfect) is that it has lost a bit of the original matt finish. It does not glare in your face, though. He reckons it needs some time for it to go back to a more matt finish, by wiping with a lightly damp cloth every now and then.
He gave the same treatment to the nero door panels.
He used Kiwi Parade Gloss... black of course; he told me it was the product he routinely used on his parade boots. Ha!
Looks nice. Will ask him to take a couple of pics and I'll post them here.
TBH, don't have a clue as to where that comes from. Would not attempt re-dyeing (save using a product which can eventually go off, such as shoe polish) and will not try to rub it hard with leather cleaners or similars, as in my friend's case it did not get away and you risk damaging the hide.
Hope this helps. Ed.
