The world has a lot of natural gas and not nearly enough crude
oil. To address the imbalance, some companies have tried to
convert the gas into a liquid that can substitute for refined
oil products like gasoline and diesel, but the idea has not
taken off in this country. It may be simpler to convert vehicles
instead and have them burn natural gas instead of gasoline or
diesel. This logic has become stronger as the price of oil has
risen on the global market and the price of American natural gas
has declined. Lately oil has been trading at around $100 a
barrel, but the same amount of energy can be bought for about
$15 as natural gas when that fuel is trading in the range of
$2.50 per million B.T.U.’s, as it has recently. (An average
barrel is 5.8 million B.T.U.’s.) Few car drivers will buy a
natural gas vehicle, however, because it is hard to find places
to fill it. One of the most successful natural gas cars, from a
technical standpoint, was the Ford Crown Victoria, which had a
trunk so large that even with n