The results show that the lactones produce less soot than conventional fuels even when accounting for the differences in heat of combustion-i.e., even though a greater quantity of the lactones must be burned to perform a given amount of work, the total soot production is lower. All the lactones have a YSI/LHV at least 50% lower than the diesel fuel and at least 30% lower than the Jet A fuel. Most of the lactones also have lower YSI/LHV than all the TG fuels-the exception is 4-5-L, which has a slightly higher value than TG alkylate, an alkane-rich gasoline. But even 4-5-L has lower values than the other TG fuels, including TG E30, which is a conventional gasoline containing 30% ethanol.