My tank had about a quarter inch layer of slimy scum coating the entire bottom third of it and was behaving as described. In my opinion, cleaning such contamination with B100 will be a long, frustrating path compared with pulling the tank, cleaning it, and putting it back in. Its also very nice to you know you really do have a clean tank and you won't have to worry about mystery crud coming loose over the next few years. Also, this car was owned by old people who never ran anything but diesel, so WVO was not to blame in that case, though it will crud up a tank much quicker. I suspect they just let it sit for a long time and let bacteria proliferate along with byproducts of hydrocarbon breakdown, which is not the same thing as WVO polymerization.

Do yourself a favor and pull the tank. The interior is reasonably accessable to long brushes and degreaser. Just be sure and dry it good before reinstalling.

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1983 CD
1958 Studebaker Packard (being resuscitated)