The use of tetrahydrobenzoxazines I where R1 is a hydrocarbyl radical and R2, R3, R4 and R5 are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals, and where R2 to R5 may also form a second and a third tetrahydrooxazine ring, with the proviso that at least one of the substituents has from 4 to 3000 carbon atoms and the remaining substituents, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms, as stabilizers for stabilizing inanimate organic material, especially turbine fuels, against the action of light, oxygen and heat.