Engine performance, exhaust emissions, and cyclic variations in a lean-burn SI engine fueled by gasoline-hydrogen blends

► Effect of adding a small amount of hydrogen to a lean-burn gasoline engine is examined. ► Engine performance characteristics and exhaust emissions are studied. ► Cyclic variability of the indicated mean effective pressure (IMEP) is studied. ► The IMEP time series are analyzed using a continuous wavelet transform. ► Results reveal that a small amount of hydrogen addition can offer some important advantages.