One of our major goals at Washington State Ferries over the last several years has been achieving voluntary compliance with MARPOL 2000, a set of stringent international standards to reduce marine pollution. Part of this effort includes making our diesel engines more efficient. There is technology to accomplish this task, but since we are a state agency with a fixed budget, the cost of this effort has to be offset by finding savings somewhere else. Even for something as desirable as pollution control, raising our operating cost was not an option. Our customers are mostly daily commuters who depend on the State of Washington for reliable, low-cost transportation. Fortunately, for the performance trial described below, we selected a technology that has its own element of payback.