These are from a leading rubber manufacturer. As it explains in the
information below, spray onto a rag rather than directly onto the rubber
surface. Often the propellant in the can will cause damage as it is
normally highly flammable.
Bill
MAINTAINING RUBBER
To give your rubber that clean new, jet black look, start by cleaning it
with mild soap and water. Follow with a protectant (Armorall) or even a
silicone-based furniture polish (e.g. Lemon Pledge). Do not spray
protectants directly on the rubber. Rather, apply it to a damp rag then wipe
it on.
Some rubber will naturally bleed paraffin, which will look like hardened
candle wax. Use a solvent to carefully remove any visible paraffin.
RUBBER ENEMIES
Rubber contains plasticizers that eventually "evaporate" from rubber,
leaving it hardened and cracked. This is a naturally occurring process, but
heat, sunlight, smog, chemicals and gasoline/oil can shorten the life of
rubber parts.