Gasoline fuel formulation having a laminar burning velocity SL which is equal to or below that of isooctane at a pressure of 1 bar, a temperature of 300 K and stoichiometric air/fuel mixture strength. The formulation can be used to reduce pre-ignition in a turbocharged spark ignition engine, in particular when operating with an inlet pressure above 1.5 bar absolute. The formulation can thus also be used to reduce engine damage. The invention also provides a method of preparing a gasoline fuel, by mixing gasoline fuel components to achieve a laminar burning velocity SL for the resultant mixture which is equal to or below that of isooctane at a pressure of 1 bar, a temperature of 300 K and stoichiometric air/fuel mixture strength. It further provides a method for selecting a gasoline fuel for use in a turbocharged spark ignition engine, based on its laminar burning velocity SL.