McLean is Emeritus Director of the Combustion Research Facility (CRF), a Department of Energy User Facility at Sandia National Laboratories/California. In addition to the CRF he was responsible, under Sandia's Energy and Infrastructure Assurance mission area, for overall program management of Sandia's energy efficiency research programs. He worked in close association with the U.S. DOE research programs sponsored by the DOE Office of Science and DOE Office of Energy Efficiency and Renewable Energy. McLean received his undergraduate and graduate education in mechanical engineering at the University of California, Berkeley and was associate professor of mechanical engineering at Cornell University before joining Sandia in 1978. His past research has involved coal combustion, flame chemistry, engine combustion and alternative fuels.

McLean was a member of the Public Interest Energy Research Independent Review Panel, 2003-2005.