Lithium grease is petroleum based, it's not recommended for use around plastics and rubber where it'll cause these to prematurely fail. Silicone grease, on the other hand, works better in low temperature, low stress applications around plastics and rubber.

Lubrication of seals can be achieved by adding a lubricant to the rubber compound before molding, or by treating the seal after molding. Seals that have a lubricant molded into them are considered to be internally lubricated. Silicone oil or molybdenum disulfide can be applied to the surface of molded rubber products.

Silicone lubricant safely lubricates, waterproofs and protects metal and non-metal surfaces such as rubber, plastic and vinyl. Silicone grease is safe on rubber and actually helps to keep it soft. Any other grease with a mineral oil base will degrade natural rubber.