Your fuel filter is a single flair or O-ring design. The threads job is not to seal it is to hold the taper\o-ring in place. There is no seal between the fitting and the steel line so even if you did get none sealing threads to seal the fuel would just come out between the fitting and the line.
You need to look at the condition of the flair and threads going to the filter and look for any dirt. 90% of the time we get “leaking filter” at the dealership it is because of cross threaded fittings. 8% of the time its dirt\damaged O-ring and the other 2% is defective filters/or defective flair. As a general rule the filters are not as hard as the factory fitting so if you cross threaded it most time a new filter will fix you up.
Also I am not a huge fan of Teflon tap on the wrong side of the fuel filter. The tape is made up from strains and those strains can come lose and end up in you injectors or regulator. No amount of fuel injection cleaner will get them out.

Of course the above percentages are complete guess. I did not keep a running tab on every job.

 

So should I just clean it incase theres dirt? Check the O ring?