We switched our entire fleet of diesel trucks over to dual fuel and the performance was dismal at best. Fuel economy dropped to 1 mpg.

Not only that it cost us 1 million dollars to do the conversions and add an LNG re-fueling vessel. Needless to say we bailed out of it as soon as the Bush administration relieved the rules.

Natural gas lacks the BTU's for true diesel power. To travel any distances you must carry huge quantities of LNG. I see city buses that run on CNG, but they are close to a refueling point. I don't think you want CNG just to be able to tool around town a few miles. My opinion is it is not a viable option, yet.

Not only that, try and locate a LNG refueling station. We had to have our LNG brought all the way in from Texas on a huge tanker to refill our huge vessel.

PS- Can an LP tank hold pressure for compressed natural gas? I'd check that legality out first.