Tank Cap Seal Failure

This week, I noticed that the lid on my oil-filled tank cap was lifting 
off the container.  I have a 15 gal rubbermaid PP container with 
snap on lid.  During construction, I used GE Silicone II Window and 
Door sealant to secure the lid and I have had no problem until now, 
a couple months after completion.  The guys at the hardware store 
assured me that this stuff was oil-proof, but maybe not.

Now I must reseal the lid.  Is there a better sealant to use?  Any 
tips for making sure it sticks this time?  Even after I clean the 
surfaces, there will still be oil residue, so can the new coat of 
sealant adhere to the surfaces?

Matt Behrend