Compact plasmatron devices can provide important new possibilities for reducing engine pollution, making use of alternative fuels and increasing the engine efficiency. These improvements involve the use of the plasmatron as a compact, rugged, rapid response and highly flexible means of converting a wide range of hydrocarbon fuels into hydrogen rich gas onboard a vehicle. Opportunities for engine operation with a greater variety of fuels and fuel combinations could be significantly increased by use of plasmatron devices. In addition to the capability of using alternative fuels, large reductions in pollutant emissions from SI engines are possible. Very lean operation, by hydrogen addition to the main fuel, can reduce NOx production by large factor relative to stoichiometric combustion without a catalytic converter, and provide a reduction of more than a factor of ten relative to operation with a three way catalytic converter at stoichiometric air to fuel ratios. Substantial NOx reduction could also be obtained by heavy exhaust gas recirculation (EGR), facilitated by use of hydrogen-rich gas with stoichiometric operation of the engine.