In one exemplary embodiment of the invention, a method of regenerating a particulate filter includes flowing an exhaust gas from an internal combustion engine into a particulate filter and determining a particulate level in the particulate filter. The method also includes performing a primary regeneration when the particulate level is below a first value, the primary regeneration including flowing exhaust gas with a selected amount of hydrocarbons in the exhaust gas into the particulate filter, and performing a secondary regeneration when the particulate level is above the first value, the secondary regeneration including flowing exhaust gas with an increased amount of nitrogen oxide into the particulate filter.