1995 Chevy Blazer Strange Leak

Engine Mechanical problem
1995 Chevy Blazer 6 cyl Four Wheel Drive Automatic

After discovering water in a recent fuel purchase and having an auto tech associated to my place of employment, change the fuel filter and add vavoline water remover, the auto tech decided to rev the engine in an idle position for a lengthy time to supposedly get the new fuel and water remover that he'd added, into the engine, then a mysterious lava like substance started leaking from under the rear of my vehicle. The auto tech seemed to think the lava like material was leaking from a hole in something called a crossbar under my vehicle. The material was similar to hot oozing lava and when it cooled was like a brownish black resin of some sort that remained pliable and doesn't emit a smell. Does anybody have any information as to what was oozing from my vehicle?