NGL are the liquid hydrocarbons produced with or stripped from Natural Gas. These would include propanes, butanes, and other similar liquids. A napthinic type liquid is also often produced with natural gas. The field hands that work around gas wells will (would in the older days) mix it with gasoline in their vehicle fuel tanks. I don't know if that practice goes on today or not.
LNG is natural gas that is liquified via a refrigeration process to change its state from vapor to liquid. LNG can be liquified with or without NGL's in it, and more often than not, it is liquified with NGL's included. Those have to be stripped out somewhere in the process so that the gas can be used as certain types of fuels.
NGL (natural gas liquids)
Natural gas liquids are those hydrocarbons liquefied at the surface in field facilities or in gas processing plants. Natural gas liquids include ethane, propane, butanes, and natural gasoline.
LNG (liquefied natural gas)
The light hydrocarbon portion of natural gas, predominately methane, which has been liquefied. LNG is natural gas in a liquid form. Its temperature is usually less than -100 Degrees F.
No, using straight NGL's in a car won't work because of all the molecules lighter than butane will just boil away. In the old days, we would "weather" the NGL letting those butanes and lighter evaporate. The remaing natural gasoline had about 75 octane, what a ride in your junker car with 8 to 1 compression ratios. To stop the car after driving, you got out, open the hood and put a piece of wood over the air intake because the engine was dieseling.
In the eary 80's, the tax man figuired it out and the back taxes on the fuel used was reason enough to stop this practice.
Dcasto, I had forgotten about the problem with the casing head running on when you tried to stop the engine. Back when I messed with it, you just put the car in gear (a high one) and dumped the clutch to stop the engine.
I note that there was a news article on Energy Central just this morning about 17 people being arrested in the NE Texas area for stealing condensate from NG well sites. So someone is still interested in this stuff.