This fuel makes the ship it is used in very fast indeed. Its affects last for one standard day. To use the Schwartz, you must be either on the Up Side or the Down Side. There are two sides to every Schwartz. Schwartz users of the Up Side progress as a real Jedi would.
All powers are one difficulty higher.
There are no advantages to the Down Side. The Up Side is more powerful, but not necessarily good. Each Schwartz, of course, has both sides. What this means, is while Lone Starr may have been Schwartz-sensitive to the Up Side, there will now be a Down Sider somewhere for him besides Dark Helmet, because Dark Helmet was the Down Side of Yougurt's Up Side. This provides GMs with a good excuse to make cheap bad guys.