An antiknock additive which is a mixture of an aromatic amine, an antioxidant, the straight-run naphtha cut of naphthene-aromatic base crude oil, and chloro-and isoparaffins, is proposed. The additive is given antiknock activity by passing it through a catalyst - manganese -at the boiling point and atmospheric pressure. In a concentration of 0.03-0.2 wt. %, the additive increases the motor octane number of low-octane motor fuels by 5-14 points.