the "biocide diesel", will kill stuff in your tank but will produce a lot of dead Bodies that will plug up your filters.
This leaves you with a choice of changing a lot of filters afterwards until they are gone or pulling out the Fuel tank and havine it cleaned. Some of the biocides claim they have an enzyme/s that break up the dead Bodies.

Cleaning the Tank Filter is the easiest part of the problem.

There must be more detailed info on this in the do-it-yourself, DIY LInks under the Resources tab at the top of the page.

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84 300D, 82 Volvo 244Gl Diesel