I don't use this stuff, but I DO use a "sludge dissolving" additive to my home heating oil tank. This is a common practice in New England by those who use heating oil.
I have been using the Home Depot brand, but am switching to STR-2+.
I measure the fuel level with a stick (since the gage does not work) and I can feel the sludge near the bottom of the tank as I take my measurement.
I can say that over the past 7 years that I have owned this house the sludge level has reduced significantly based on the feel of the measuring stick.
I have not and do not plan on using anything like this in my boat tank.