Related by context. Frequent words. (Click for all words.) 75 internal combustion 75 combustion engine 75 internal combustion engines 62 combustion engines 60 electric motor 59 diesel engine 57 diesel engines 56 hybrid powertrain 56 turbocharging 56 diesels 55 electric propulsion 55 fossil fuels 53 hydrogen fuel 53 electrically powered 53 diesel 52 diesel powered 52 electric motors 52 hydrogen powered 52 powerplants 51 hydrogen 51 alternative fuels 51 exhaust emissions 50 fossil fuel 49 PHEVs 49 EVs 49 combustion 48 cleaner fuels 48 PHEV 48 V8 engine 48 Volt 48 manual gearbox 47 gas guzzler 47 powertrains 47 carburetors 47 carbon emitting 47 electric hybrid 47 naturally aspirated 47 turbocharged 47 lithium ion battery 47 cylinder engine 46 horsepower 46 zero emission 46 hybrid electric 46 ultracapacitors 46 #.# liter V8 46 turbocharger 46 flex fuel 46 Tesla Roadster 46 powerplant 45 drivetrain 45 Chevy Volt 45 gas guzzling 45 tailpipe emissions 45 E# ethanol 45 battery powered 45 EcoBoost 45 powertrain 45 electrics 45 supercharger 45 bio ethanol 45 hybrids 45 lithium ion 45 #.#L [001] 45 nickel metal hydride 45 propulsion 45 gas guzzlers 44 engine 44 motors 44 alternative energies 44 Civic Hybrid 44 regenerative braking 44 acid batteries 44 turbo 44 electric 44 Chevrolet Volt 44 engines 44 supercar 44 pistons 43 V6 engine 43 hp 43 wall socket 43 particulate emissions 43 cleaner burning 43 automobiles 43 lithium ion batteries 43 cylinder diesel 43 CO2 emissions 43 #bhp [002] 43 electric hybrids 43 CAFE standards 43 flywheel 43 renewable fuels 42 Toyota Prius 42 fuel 42 compressed natural 42 fuel injectors 42 Toyota Prius hybrid 42 supercars 42 variable valve timing 42 incandescent bulb 42 Ford Escape Hybrid