1. A method of controlling an exhaust stream temperature at a point along an exhaust system including an oxidation catalyst, a particulate filter including an outlet, and a fuel injector for injecting fuel into an exhaust stream at a location upstream from the outlet of the particulate filter, the method comprising the steps of: providing an oxidation catalyst model; monitoring a condition of an exhaust stream; calculating a hydrocarbon fuel injection flow rate for the fuel injector based on the oxidation catalyst model; controlling an operation of the fuel injector based on the calculated hydrocarbon fuel injection flow rate, to control the exhaust stream temperature at the point along the exhaust system; determining an error in the oxidation catalyst model based on the monitored condition; and changing the oxidation catalyst model to reduce the error.