This program consisted of conducting an experimental program on a heat recovery heat exchanger exposed to the exhaust gas stream of a nominal 300-horsepower, truck-size, diesel engine. Investigations were made to evaluate the effects of gas-side fouling and sooting on the vapor-generator performance in the exhaust of an engine using standard No. 2 distillate fuel with and without a fuel additive. The effectiveness of various clean-up schemes was also evaluated during these tests.