General Motors has turned to the University of Tulsa in Oklahoma for help developing lean burn engines with copper zeolite catalysts to meet tough new U.S. emission standards. Lean burn engines are more fuel-efficient than standard petrol engines because they burn higher ratios of oxygen to fuel, but they can't meet new U.S. pollution standards that will be in effect in three years, says Richard Blint, a senior research scientist with the chemical and environmental sciences lab at GM's research and development centre in Michigan.