Fuel polishing WILL NOT work effectively if the tank walls have thick
films of deposited sludge ...and are not cleaned FIRST.
Polishing does not remove the sludge from the walls.

In article , Gordon
wrote:

Neighbor just opened a fuel polishing business. He had a cruising
sailboat yesterday that is planning to circumnavigate and decided to
clean his tanks.
Those tanks were full of the nastiest stuff! Even big chunks of gunk.
So if you are having the slightest filter problems, I'd look at
polishing. It ain't cheap, but is good insurance.
Gordon