NG & Diesel make a 39% efficient engine
 

Super efficient combustion engine emits half the carbon dioxide

Super Efficient Combustion Engine Emits Half the Carbon Dioxide
ETH researchers redesigned the conventional diesel engine of a VW Golf to run on 90 percent natural gas. (Credit: Tobias Ott / ETH Zurich)

The combustion process in a Diesel engine is naturally more efficient than in a spark-ignited engine, the only problem is that regular Diesel fuel is not exactly as clean-burning as some lighter fuels...