Related by context. Frequent words. (Click for all words.) 63 exhaust emissions 60 particulate emissions 60 NOx emissions 57 emissions 57 greenhouse gasses 57 CO2 emissions 56 nitrous oxide emissions 56 tailpipe emissions 55 carbon dioxide emissions 55 air pollution 54 pollutant emissions 54 greenhouse gas emissions 54 greenhouse gases 53 greenhouse emissions 53 carbon emissions 53 C# emissions 53 CO2 emission 53 CO2 53 VOCs 53 pollution 52 GHG emissions 52 greenhouses gases 52 emission 52 particulates 52 NOx 52 particulate matter PM 51 Emissions 51 nitrogen oxides 51 nitrogen oxide emissions 51 NO2 51 Co2 50 GHGs 50 combustion engine 50 carbon dioxide emission 50 pollutants 50 nitrogen oxide 49 carbon dioxide CO2 emissions 49 Carbon dioxide emissions 49 airborne pollutants 49 particulate matter 49 turbo lag 49 exhaust fumes 48 carbon dioxide 48 internal combustion engines 48 diesel exhaust 48 carbon emitting 48 combustion 48 carbon emission 48 harmful toxins 48 CO2 emitted 47 harmful pollutants 47 particulate pollution 47 greenhouse gas 47 greenhouse gas GHG emissions 47 pollutant 47 volatile organic compounds 47 fine particle pollution 47 smog 47 carbon footprint 47 harmful gases 46 carbon dioxide CO2 46 aerodynamic drag 46 heat trapping carbon dioxide 46 air toxics 46 particulate filter 46 internal combustion engine 46 fossil fuels 46 drivability 46 reducing carbon emissions 46 combustion engines 46 Greenhouse gases 46 diesel fumes 46 fine particulates 45 greenhouse gas emission 45 greenhouse gases emitted 45 carbons 45 carbon dioxide emitted 45 water vapor 45 driveability 45 Carbon Dioxide 45 fossil fuel 44 CAFE standards 44 diesel 44 traffic congestion 44 lubricity 44 polluting 44 burning fossil fuels 44 carbon footprints 44 reducing CO2 emissions 44 internal combustion 44 congestion 44 paved surfaces 44 carbon emitted 44 mileage 44 oxidant 43 heat trapping emissions 43 idling 43 ozone 43 ethanol blends 43 PM#.# 43 refined sugars