Related by context. Frequent words. (Click for all words.) 61 tailpipe emissions 51 CAFE standards 49 greenhouse gas 49 Average Fuel 49 exhaust emissions 49 emissions 49 greenhouse gas emission 49 greenhouse gas emissions 48 carbon dioxide emissions 48 emission 47 GHGs 47 Fuel Economy 46 heat trapping emissions 46 greenhouse gases 46 Fuel Efficiency 46 air pollution 46 pollutant emissions 46 CO2 emissions 45 NOx emissions 45 Environmental Protection Agency 45 carbon emissions 45 C# emissions 45 mpg 45 greenhouse emissions 44 renewable fuels 44 efficiency 44 global warming gases 44 nitrogen oxide emissions 44 regulate greenhouse gases 44 Clean Air 44 EPA 44 alternative fuels 44 reduce carbon emissions 44 tailpipe 44 smog 44 nitrogen oxides 43 nitrogen oxide 43 carbon dioxide CO2 emissions 43 pollution 43 particulate emissions 43 greenhouse gasses 42 pollutant 42 Carbon dioxide emissions 42 cleaner burning 42 cleaner fuels 42 carbon dioxide emission 42 Emissions 42 reducing carbon emissions 42 regulate carbon dioxide 42 ozone pollution 42 CO2 emission 42 mercury emissions 41 Pavley 41 Clear Skies 41 greenhouse gas GHG emissions 41 mileage 41 curbing greenhouse gas 41 Automakers 41 reduce greenhouse gas 41 automakers 41 Board CARB 41 GHG 40 gas guzzlers 40 reducing CO2 emissions 40 fine particle pollution 40 regulating greenhouse gases 40 carbon emission 40 NOx 40 combustion engine 39 CARB 39 NHTSA 39 GHG emissions 39 gas guzzling vehicles 39 mercury pollution 39 CAFE 39 RX #h 39 Toyota Prius 38 Environmental Integrity 38 corn ethanol 38 Renewable Fuel 38 diesel powered 38 #g/km [001] 38 emission reduction 38 CO2 38 pollutants 38 Safety Administration 38 reducing greenhouse gas 38 gas guzzling 38 emission reductions 38 Motor Vehicle Safety 38 nonpolluting 38 carmakers 38 SUVs 37 gas guzzler 37 carbon dioxide emitted 37 carbon dioxide 37 heat trapping gases 37 Waxman Markey bill 37 zero emission 37 g km 37 Greenhouse Gas