The main fuel filter will be circa 5 micron, brand dependent. Some go down to as low as 2 or 3. So installing another filter the same as what you already have will be pointless as the filter that sees the fuel first will do all the work and the second filter will do nothing.
Ideally you would run a higher micron filter after the tank to catch the larger particles and then the secondary filter can catch the finer particles letting both filters do a job.

As for the fuel doctor. That stuff is excellent for water dispersion, however not necessarily needed on every fill but it certainly won’t hurt to use it as you never know what the next tank full from the servo may give.


Sent from my iPhone using Tapatalk