Solium
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Solium is a liquid fuel used by Colonial spacecraft, and is kept in large supply aboard Colonial Battlestars. Solium is also explosive at high temperatures and any fire near solium tanks could easily destroy any spacecraft (Fire in Space). Several ships in the fleet reported solium leaks in the aftermath of the Cylon holocaust. Apollo, Boomer and Starbuck were sent to the Gemini freighter and Rising Star to detect the harmful leaks (Saga of a Star World).
Solium is apparently a secondary fuel, perhaps used for smaller ships or equipment in place or instead of tylium.