Possibly 
  Not wishing to contradict Neil, it depends.  There was a transition period around '91 where the factory moved from the aircraft style filler and the hinged lockable job.  The only seal on these was a green o-ring which never did a complete job, and needs gunking up with lots of sealant to prevent seeping.
 
 On mine, I tried fitting the additional rubber ring ring 'twixt cap and tank and it just would not work.  I think that later cap assemblies were modified to allow the black seal as well as the o-ring.
 
 charles