Portable generator sets have been successfully used as gasoline additive screening tools for intake system deposits (ISD) and intake valve sticking tendencies. To assist in the additive development process, a program was undertaken to determine if the generator sets might also be used to examine additive effects on combustion chamber deposits (CCDs). Tests that were performed and evaluated, show that the generator set is capable of discriminating between additives and correlating with engine and fleet testing results with respect to CCDs. This has resulted in a screening test with a single test cycle that can effectively screen fuels and fuel additives for intake system deposits, intake valve sticking and combustion chamber deposits. This paper discusses the engine and fleet tests that are used to show the generator set's ability to satisfy these criteria.