That bottle of black stuff looks about the same as what came out of mine. Carbon as far as I could tell. Not so with the primary filter. Shortly after I purchased my cars I did the purge thing. Now I know what goes in the tank, so don't know if I'll do it again. Someone with a can lying about, may post ingredient list. It's very long. chomamma....I agree, not algae, but critters of some sort.

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83 SD

84 CD

Read the factory shop manual and clean your fuel system by the book. It is easy to do and if you look at the insides of an injector you will see that solvents are useless.