Policymakers are trying to cut carbon-dioxide emissions and have promoted generating electricity using solar, wind, wave converters and tidal turbines. But a larger need is to supplement petroleum, the polluting but superb transportation fuel. Ocean Thermal Energy Conversion plants operated during the past 40 years show that OTEC plants have the (1) reliability and (2) massive scale to synthesize a sustainable new global fuel to replace dwindling petroleum supplies. For reliability, we will review the experience of the two OTEC plants currently operating in Japan and Hawai’i. Both plants have demonstrated robust performance for heat exchangers and power components. This record is possible because OTEC uses components similar to typical power plant or air-conditioning machinery. Mini-OTEC generated the first net power in 1978, and it was designed and built in only a year. Today’s onshore plants easily synchronize with the grid frequency, and generate dispatchable electric power instead of the intermittent power from most renewable energy sources. Recent OTEC floating designs benefit from the offshore industry’s hull and power cable research & development. For scale, large OTEC plants operating on the tropical high seas are a feasible supply chain to make transportation fuel in globally-significant volumes. Two recent computer studies suggest that industrial OTEC will have benign biological and climate impact. In comparison, it would require 100% of the US corn harvest to furnish only 30% of US gasoline needs – with no jet fuel or diesel. The expensive drama of obtaining permits for renewable energy projects show that the land and shoreline are already crowded, yet the solar energy equivalent to seven offshore Sahara Deserts is being ignored. Finally, policies and costs supporting or hindering OTEC will be compared for eight nations and the United States, including findings by the International Energy Agency’s Ocean Energy Systems committee. These results explain the current state of this attractive ocean energy resource.