It's a little hard to find, but I like to use Permatex Super 300. It's a brush-on liquid sealer that was developed to resist aviation gasoline, and it stays flexible forever, much better than the 3-D Permatex brush-on stuff.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!