I’ve been looking into which products would be best for weatherstrip maintenance and have decided to avoid silicone-containing products altogether. Through a series of e-mails with Jano and SanDiegoMac, as well as several telephone conversations with tech support personnel at 303 Products, Inc. and DuPont, my personal choices are:

a) 303 Aerospace Protectant (with UV screening) for routine use on all exposed rubber and other select surfaces; and
b) DuPont Krytox® Lubricants for problem areas that squeak -- rubber and plastic alike -- such as the header rail in convertibles, cup holders, etc.

Proper use of 303 Aerospace Protectant requires that the areas to be treated be clean of any dirt or oils; then thoroughly wet the surface with Protectant and allow to soak for approximately five minutes (rubber) before wiping dry with a soft, lint-free cloth. Reapplication is recommended “every 30 to 80 days of exposure” or when the water repellency begins to diminish. This product is widely available at a reasonable price. Shelf life is a minimum of five years. Two sources are Autopia Car Care and Autogeek.

Krytox® Weatherstrip Lubricant may be applied after the 303 treatment, if necessary. Treatment areas for Krytox® should receive limited exposure to dust and dirt, as it may remain somewhat tacky and can attract dust; it could also rub off on clothing if applied too heavily. Unlike the 303 product Krytox® is not wiped off after application, rather a thin layer is massaged into the rubber and left in place. Available as both an oil and light grease, choice depends on area being treated and/or personal preference. Care must be taken not to get any on glass or painted surfaces, not because of potential damage but because it’s difficult to remove once it’s on there. Reapplication isn’t necessary nearly as often as with 303 Aerospace Protectant. Distribution is rather limited and cost is quite high. GM sells a 1 oz. applicator bottle for between $69 and $88 US depending on dealership pricing; among other places, it’s referenced in the “2007 Chevrolet Corvette Owner Manual” in the section entitled “Recommended Fluids and Lubricants,” under “Weatherstrip Conditioning”: “GM Part No. U.S. 3634770, in Canada 10953518.” Also recommended is “Dielectric Silicone Grease (GM Part No. U.S. 12345579, in Canada 992887)”; more about silicone in a moment. Chrysler dealerships sell the same one ounce bottle of Krytox® Weatherstrip Lubricant -- MOPAR Part No. 04773427 -- for about $85 US, and the Volkswagen offering costs even more. Online sources include GM Parts Direct (enter Part #3634770), where the GM product sells for $41.34; and Eckler’s, where a small tube of “Krytox® Weatherstrip Saver” grease (Item #A2524) sells for $44.99. Jaguar endorsed use of Krytox® fluid for interior squeaks ten years ago as outlined in Service Advisory “910-01 APR 98.” Shelf life is indefinite.