Excise taxes are taxes paid when purchases are made on a specific good, such as gasoline. Excise taxes are often included in the price of the product. There are also excise taxes on activities, such as on wagering or on highway usage by trucks. Excise Tax has several general excise tax programs. One of the major components of the excise program is motor fuel.
It sucks that they're taxing what every person needs to do to live, except for those who can successfully live under the table, but that doesn't mean it's necessarily unconstitutional or beyond the taxing power of Congress.
If it isn't a direct tax, then I don't know how anyone could argue any other form of taxation is direct. Anytime I sign a check to the Dept of Treasure, I would consider it a direct tax.