Re: Diesel fuel economy is a lie . . .
CNG and Propane are doable on just about any internal combustion engine, even diesels. Ask QC, he is an expert.
I will say this about the two.
CNG
1. Has about 65% of the BTU's of gasoline when comparing gallon to gallon.
2. In an automotive application, range suffers greatly.
3. CNG must also be pressurized to 3600 psi. to get enough on board to be useable.
4. CNG does NOT fire off in extreme cold.
Propane
1. Propane is about one to one (with gasoline) on performance, BTU's and is a low pressure gas.
2. As mentioned, propane does not like EXTREME cold.
Two of the US automakers entered the propane and CNG market about six years ago. They produced the vehicles for the gaseous fuel party and nobody showed up. Less than 10,000 vehicles were sold per year (combined) in a 15 million vehicle per year market.
Honda makes a CNG vehicle and has sold about 2000 per year. It is a terrific LOSER for them.
It costs MILLION$$$ to certify an engine family, on a new fuel, for "on road" automotive use (cars and trucks under 10,000 # GVW).
REAL interest has to be there, with real commitments, for automakers to go down that road again.
I'm not saying they won't. The technology is there and even some of the hardware. However, any new offering(s) would have to be re-certified for 2010 and 2012 emissions laws (EPA). Not to mention re crash testing every vehicle model for new NHTSA standards for 2012.
If you were making the product decisions-WOULD YOU?