Have you tried Lexol Leather cleaner?...I have used it on my leather hat...which sees all kinds of dirt.
Have you contacted BMW. The Germans have probably figured out a solution for everything.
I wish pollen stains were all that are on my truck seats. Own horses and dogs and see how they look. But they do hide any other stains that happen to come along.
I think going to a detailing shop where they clean autos or even the dealership may have some things that you can use so you do not mess up the leather.
I would try saddle soap it cleans just about everything off our show saddles. And they can get quite messy after a day of showing or trail riding.
Maybe the BMW will give birth to a hybrid car now that it has been fertilized.
It will run on solar energy, love the rain, and smell good , all while decorating your driveway.
Their is a product that we have used for twelve years made by a company in your neck of the woods.
The product is called SEM soap made by SEM. Use this in conjunction with a 3M "GRAY" scuff pad only.
If this does not work then you will probably need your seats lightly dyed.
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