Disclosed herein are methods for operating a reformer and for operating a vehicle. In one embodiment, the method for operating the reformer comprises: introducing an oxidant and fuel to a reformer at greater than or equal to about 25,000/hr space velocity; combusting the oxidant and the fuel the reformer to produce a combustion gas, wherein the reformer comprises a reformer substrate comprising a reformer catalyst and having a thermal conductivity of greater than or equal to about 35 W/m.degree. K; extinguishing the combustion; and introducing additional fuel and oxidant to the reformer at an air to fuel weight ratio appropriate for reforming. A method of using the reformate produced to reduce cold start emissions and/or regenerate an exhaust control device is also disclosed.