Gray Paste/Material Connecting Fuel Filter to Pipe?

I own a 2001 Chevy Impala, and wanted to try changing my fuel filter, but when I got underneath the car I noticed that there was a hard gray paste/material in the threads that connected the outgoing pipe to the fuel filter. I assume it's something to help seal the connection, but does anyone know exactly what it is before I remove the filter and replace it? Any info appreciated, thanks!
Gray Paste/Material Connecting Fuel Filter to Pipe?
It is a locktite sealer more than likely. A tube may even come in the fuel filter box. If not ask for a small tube of it.
Gray Paste/Material Connecting Fuel Filter to Pipe?
It's probably teflon paste, I like it better than the teflon tape, get it at any hardware or auto store.
There's one more possibility. When a petroleum product mixes with water it turns into a grey fluid. If the fuel filter has been leaking a little and mixing with water from the road this could occur.
someone probably used plumbers glue, maybe the threads are stripped, or they didnt put a new o-ring on when they replaced the filter. you can also use plumbers tape and wrap the threads too, if it still leaks.