<p>A motor fuel comprising 35-98% hydrocarboncontaining base and 2-65% by volume of an additive which comprises a mixture of at least two ethers containing (a) 0-90% by volume of methyl tert-butyl ether; (b) 0-90% by volume of isopropyl tert-butyl ether; and (c) 0-90% by volume of sec-butyl tert-butyl ether, has a high octane number and reduces exhaust pollutants.</p>
