Yeah natural gas is good and if you have to use traditional fossil fuels diesel gets you the most bang for your buck in terms of energy efficiency. What the snooty electric vehicle people don't realize is most of the time, in this country at least, all or a great chunk of their electricity is generated using fossil fuels. Lots of your energy yield gets lost converting it to electricity and then into a battery which is then used by the car. You would create less net emissions just using the fossil fuels as your primary fuel source.