I've had Krown done here on my 2013 Kia Optima every year since it was new. So far it's swelled and destroyed half a dozen rubber parts including all the door handle seals (2 sets), seals under the hood (replaced twice), the rubber cover and seal for the trunk release switch (missing for a year now) and the dampers under the trunk door.
The problems seemed to start after a change in product the second year I had it applied. The owner denied there was a change, but the first year the product was tarry and didn't run. The second year, I couldn't keep the car clean, the product was thin and oily and didn't stay in place. That's when the rubber parts started to disintegrate.
My dealership has suggested I stop having a car treated. I'm looking right now at several hundred dollars in repairs and parts replacements due to the Krown product.
I have mixed feelings about the staff here. I don't believe they are aware that their product destroys rubber parts, and it probably hasn't always done so. They're clearly not customer-service oriented people, and they tend to raise a fuss if you bring your car in without first taking it through a car wash. I've found the owner downright rude at times, and he doesn't seem to place much value on his customers' time or understand that not everyone has a garage to work on cars.
Several times, I've tried to get the chip and buff service done and have been given the run-around. On one occasion I was asked to bring the car in to be approved for the chip and buff and was kept waiting for an hour while the owner chatted with a friend on the phone, burning through my entire lunch hour.
In four years, I only managed to get them to book me in for chip and buff once, despite asking about it every year, and that was after some negotiation. One of the excuses given was that his friend's boat would be occupying the garage for the next two weeks, an excuse which was only believable due to the fact that I'd literally just overhead him talking to his friend about storing his boat there. It felt to me like they weren't interested in doing the work, even through the service costs north of $300.
Given everything, especially its effects on the rubber parts, I don't believe I will have Krown applied again, and if I do, it will be at a different outlet.