Tiny -
Now you've peaked my paranoia. I'll keep an eye on it. (Just hope the leak doesn't start while I'm driving!)
Jerry and Grigg suggested
cork/rubber for the gasket. I believe that the original gasket was cork, but the cork particles were smaller than the ones in my new gasket.
The cork/rubber swells and shrinks a lot. I'll change to rubber if leaks develop. Any suggestions about what to use?