Comments from my uncle Rick:
Don't get me started! Diesel Rules! Actually I believe the "law of diminishing returns" has kicked in on highway diesel engines. Environmentalists seem to be focused on the exhaust stack and not the efficiency of the engine. The engine now has to burn more fuel and oil change intervals increased (and they don't hold a few quarts of oil they hold cases)with the technology of putting less particles in the air.
So with a life expectancy of 1-mil. miles, you lower the MPG by .5 mpg and double the oil change interval - did you help or hurt the environment? Grand Pa Sheehan got 50+ MPG from his Volkswagen Rabbit Diesel back in the late 70's! Last but not least - Diesel Fuel delivers a high BTU. Converting the fuel to energy - others fuels don't produce the energy this fuel does (for the $). Thanks for letting me rant!