Look for O-RING Lube.. It is Silicone Grease and should be available @ Big Box HW and I know you are up north, so it may not apply, but Swimming Pool Supply Stores carry that as well..Hay I also get that grunting sound too after I apply it on and open/close roof. You'd think the lube would be the last thing that would cause grunt sounds but i've notice it too.
I'm thinking a silicone grease would last longer, but I was unable to find such a product in my local hardware stores. I'll stick to this spray for the meantime as it's cheap and will last for many applications.
Super Lube 3 oz. Tube Silicone Lubricating Grease with Syncolon (PTFE)-92003 - The Home Depot