The use of imidazolium salts (I) where R1 and R3 are each independently an organic radical having 1 to 3000 carbon atoms, R2, R4 and R5 are each independently hydrogen or an organic radical having 1 to 3000 carbon atoms, X is an anion and n is the number 1, 2 or 3 as additives for fuels, especially as detergent additives for diesel fuels, as wax antisettling additives for middle distillate fuels and as lubricity improvers, and for improving the use properties of mineral and synthetic nonaqueous industrial fluids.