During the testing in May 1972, it was determined that the TCCS-powered M-151 vehicle met 1976 Federal emissions standards. Since the time a 50,000 mile durability test has been conducted on this vehicle by Texaco under contract with the U.S. Army. Although major engine and emission control system maintenance was required during the mileage accumulation, Texaco claimed 1976 emission levels were maintained. Included in the maintenance was: four individual replacements of various catalytic elements in the system; several ignition modifications; EGR system cleaning; and major valve train maintenance. As part of EPA's cooperative effort with the U.S. Army and EPA's continuing interest in the emission characteristics of this engine concept a confirmatory test program was scheduled in the EPA laboratory.