A process for the alkylation of alkane with olefin or olefin precursor such as an oligomer of tertiary olefin comprising contacting a liquid system comprising acid catalyst, isoparaffin and olefin in concurrent downflow into contact in a reaction zone with a disperser mesh under conditions of temperature and pressure to react said isoparaffin and said olefin to produce an alkylate product is disclosed. Preferably, the liquid system is maintained at about its boiling point in the reaction zone. Unexpectedly, the olefin oligomers have been found to function as olefin precursors and not as olefins in the reaction. Thus, for example, a cold acid alkylation using an oligomer of isobutene (principally dimer and trimer) with isobutane produces isooctane with the isobutane reacting with the constituent isobutene units of the oligomers on a molar basis. The product isooctane is essentially the same as that produced in the conventional cold acid process.