This　study　investigated　effects　of　dimethyl　ether　addition　on　the　gasoline　engine　combustion　and　emissions　performance　under　idle　and　stoichiometric　conditions.　The　engine　was　first　modified　to　be　fueled　with　gasoline　and　dimethyl　ether　simultaneously.　The　experimental　results　showed　that,　with　the　increase　of　dimethyl　ether　energy　fraction　in　the　total　fuel,　the　total　fuel　energy　flow　rate　was　decreased,　and　the　flame　development　and　propagation　periods　were　shortened.　The　cycle-to-cycle　variation　was　reduced　and　the　degree　of　constant　volume　combustion　was　increased　after　the　dimethyl　ether　addition.　The　dimethyl　ether　blending　was　beneficial　for　reducing　hydrocarbon　and　nitrogen　oxide　emissions　from　1951　and　95　ppm　of　the　original　engine　to　552　and　34　ppm　of　pure　dimethyl　ether,　respectively.　Meanwhile,　with　the　increase　of　dimethyl　ether　addition　level,　the　peak　cylinder　pressure　and　carbon　monoxide　emission　were　decreased　at　first,　whereas　increased　when　the　dimethyl　ether　energy　fraction　exceeded　49%.　Furthermore,　heat　release　rate　during　the　low　temperature　reaction　was　enhanced　with　the　increase　of　dimethyl　ether　addition　level.　The　maximum　heat　release　rate　was　heightened　and　its　relevant　crank　angle　was　advanced　during　the　high　temperature　reaction,　period　after　the　dimethyl　ether　enrichment.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.