Ive had my UW seats in a model x for almost 2 months and have put 5000km on it. Two kids, 5 months and 8 years old.
I clean my car inside and outside every week. Not because I have to but because I like to
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They get marked up a little bit as far as smudges go or if a kids foot hits the seat but literally all it takes is a quick wipe with a damp microfiber cloth and it's good as new. I even somehow had blue ink on one of the back seats after giving my nieces a ride. I'll admit it scared me when I saw it but it wiped away with a baby wipe instantly.
I would NEVER, and I mean NEVER, use a magic eraser on the seats. Its way too abrasive and totally unnecessary from my experience. I have no facts on this but believe it will absolutely take off any long term protective coating. Stay away.
I haven't had to use it but the manual is pretty clear for trickier stains:
Polyurethane Seats
Wipe spills as soon as possible using a soft cloth moistened with warm water and non-detergent soap. Wipe gently in a circular motion. For difficult stains on ultra-white seats, use isopropyl alcohol, then wipe with a damp cloth. After cleaning, allow the seats to air dry.
I don't let my kids, or anyone else, eat in the car. We eat before we go, when we supercharge, or when we arrive. This isn't because of ultra white, I personally think eating shouldn't just be done anywhere whenever someone feels a slight urge. I know alot of people will disagree with it but it works for us. Covered drinks are fine and my 8 year old has been trained well.
They are super comfortable and easy to wipe. I'm more concerned about the stitching staining in the long run than I am the seats. So far no issue with the stitching though.
On those hot summer days the seats were awesome, not hot and uncomfortable / almost sweating feeling on my back. I love the look and would not trade them for any other color. I'd definitely order them again.
If you see a mark or mess wipe it up. If it doesn't come up follow the manual. I haven't had to use isopropyl alcohol once yet. Everything wipes up with a damp microfiber so far.