Petroleum Institute's Committee on Environmental Affairs, and the board of directors of the MIT Corporation.
Dr. Clewell maintained membership in several professional societies, among them the Society of Automotive Engineers, the American Physical Society, the American Association of Petroleum Geologists, and the Society of Exploration Geophysicists. He was also a fellow of the Institute of Electrical and Electronics Engineers.
Dr. Clewell received the Environmental Conservation Distinguished Service Award from the American Institute of Mining, Metallurgical, and Petroleum Engineers in 1974.
Retiring from Mobil in 1977, Dr. Clewell remained involved in the direction of energy research, promoting coordinated efforts to develop a technology base to meet the energy needs of twenty-first century civilization. "It's still such a challenging industry," Dr. Clewell remarked not long after retirement. "There are many technological advances to be made to decrease the risks . . . although it's those very risks that make this business an adventure."