An improved process for reacting crude aqueous methanol feedstock with iso-olefinic hydrocarbons to produce C.sub.5.sup.+ methyl tertiary-alkly ethers, which comprises: contacting the aqueous methanol feedstock with a liquid hydrocarbon extractant rich in C.sub.4.sup.+ iso-alkene under liquid extraction conditons; recovering an organic extract phase comprising the hydrocarbon extractant and a major amount of methanol introduced in the feedstock; reacting the extracted methanol and C.sub.4.sup.+ isoalkene in contact with an acid etherification catalyst under catalytic reaction conditions to produce ether product; recovering an aqueous methanol raffinate phase containing the major amount of water introduced with the feedstock and a minor amount of feedstock methanol; and converting methanol from the aqueous raffinate phase to produce hydrocarbons.