I agree with Bill D,
I had the same problem with the Meg's Endurance and their Hot Shine Tire Spray
It seems like a lot of the tire products cause the browning. These two were some of the worst for me.
I don't know whether it is the rubber changing colors or the crap that get collected by the dressing.
Browning of tires has really nothing to do with the type of dressings you use. Do a search on the web for tires and blooming. The sidewalls are designed to do that when they heat up. The brown stuff is anti-oxidizing chemicals that protect the sidewalls from UV. Some tires do it more than others. Here's another quote from Mike phillips:
"Most people don’t give a lot of thought to their tires except for, how they look. Truth be known, your tires are designed to perform under extreme conditions of heat via kinetic energy transfer, high speeds for long periods of time and incredible forces of torque and flexing.
That’s a lot to ask from a chunk of rubber, inflated with air like a cream filled donut.
The science behind the modern rubber formulas used by major tire manufactures today is both complex and interesting.
The rubber itself contains and ingredient called Antiozonant.
Antiozonant is an ingredient that helps to prevent the exterior rubber surface from cracking, checking, oxidizing, and deteriorating. The rubber is designed in such a way as to constantly work its way to the outside of the tire and as such, continually replenish the exterior surface with fresh antiozonant.
After the antiozonant works its way to the outside of the tire and is exposed to the air, it oxidizes and turns brown. The technical term for this effect is, blooming.
This is why you see a brown film on the surface your tires. You can wash your tires with soap, or an all purpose cleaner and remove this film, but in a few weeks it’s back. That’s because the antiozonant continually works its way to the outside of the tires every time you drive your car.
Because your tires contain a limited amount of antiozonants, harsh detergents and other cleaning agents should be avoided because these types of product tend to clean too well and can remove or strip the original antiozonants from the surface. Instead, use a gentle cleaner, or premium quality car wash soap.
To maintain your tires and keep them looking sharp with a deep, dark black color, Meguiar’s offers three unique tire dressings that treat the rubber with Meguiar’s own special conditioning agents as well as patented antiozonants that replenish your tires original antiozonants and keep your tires looking blacker longer than generic tire dressings and protectants. Special polymers actually penetrate and cure to the surface to form a long lasting barrier-film that protects your tires from inclement weather and exposure to corrosive elements."