tire coating/ & detailing.

[crossy]

What is it that all the used tire shops are coating the tires with to make them look super clean. It’s a dull black, but covers everything. It’s a mess because I can always see where they have been doing it. The smell I get from it is like driveway sealer and that’s my guess. It appears to be watered down and I guess if you used a latex based sealer you could thin it out. I’m sure this question will catch some people off guard, but I fix up older trucks as my hobby and I buy a lot of used tires and there are a lot of used tire shops in my area and they are all doing this now. ANYONE KNOW FOR SURE?

SECOND QUESTION-.TIRE PROTECTION FROM DRYROT CRACKS? i have asked many times what to coat my camper and trailer tires with to PROTECT them from dryrot. I KNOW it's from the sun, but other than covers what can be done. i couldn't give squat if it makes them pretty or not I just want to protect the rubber. rubber has LOTS of oil in it, so should they be sprayed with light oil??
I'm tired of buying new tires when the old one have 75% tread left. I hate sidewall dryrot and I also know that silicone based detailers are not the answer. thanx , crossy