When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
You can use Dow-Corning DC-4, which is commonly used in the aircraft industry. It's probably what GM relabels as "Dielectric grease." Available online from www.aircraftspruce.com
I'd suggest though, going to your local Scuba Dive Shop kind of place and getting some 100% silicone grease there. The stuff they sell is milder, not as sticky and will NOT attack any kind of rubber. Doesn't irritate skin either. Probably cheaper too.
I just use the silicone grease from NAPA designed specifically for weatherstripping; no need to go for that "dielectric" stuff as long as it's silicone.