fusel oil

The word "fusel" comes from German Fusel, which is used to refer to low-quality alcoholic beverages in general, especially to inferior wines and spirits distilled with inadequate equipment.

fusel oil (plural fusel oils)

1. A mixture of several higher-order alcohols (alcohols with more than two carbon atoms) formed as byproduct in the normal fermentation process. An excessive concentration, as in low-quality moonshine, causes unpleasant taste.
   • 2006, Thomas Pynchon, Against the Day, Vintage 2007, p. 849:

     many simply blamed […] the Doosra's known enthusiasms for opium, ganja, and any number of local fusel oils, singly or combined, named and nameless.

• fusel alcohol
• potato oil

• fuel oils