# 3  AC Delco Super Lube - a light, clean grease

The numbers are 10-4057 and 12371287
Image links to Amazon for further tech information

Dielectric grease is commonly suggested for stopping squeaks in the roof/windshield interface area and it works okay for a while - a short while. On the other hand, it does discolor and stain the rubber (turns it booger gray.)
There is a GM product, available at the Chevrolet parts counter, that's made specifically for the purpose of lubing such surfaces. Unlike dielectric grease, it doesn't stain the rubber and it lasts longer between applications. As I recall, the tube I bought in the summer of 2015 was around $17. It's worth it 'cause it works. Like most stuff, it's cheaper on line if you don't want it RIGHT NOW!