This study is devoted to finding new oxygenate additives improving the quality of motor fuels. Aryl butyl acetals obtained by the addition of phenols to butyl vinyl ethers are used as additives for the first time. The reaction is carried out at room temperature in the presence of catalytic (0.3-0.6 mol %) amounts of CF3CO2H and leads to the formation of the desired products in a quantitative yield. The antiknock properties of the synthesized compounds have been investigated. It has been found that synthesized aryl butyl acetals possess quite a high research octane number (RON) (up to 110) and can be promising additives to motor gasoline for increasing knock resistance, thus, the addition of 3 wt % aryl butyl acetal increases the RON of an n-heptane-isooctane mixture as model fuel and that of the AI-92-K5 base fuel by 1.0-1.2 and 0.1-0.4 points, respectively. The efficiency of the antiknock additive depends on the structure of the alkoxyl radical in the aryl butyl acetal molecule, thus, the blending ONs of acetals with a branched isobutoxyl radical is higher than the values of linear butoxy derivatives by 3.4-6.7 points. Acetals containing the methyl substituent in the phenoxy radical have higher ON values.