CNG gets further boost

Article describes a system recently introduced by the Ingersoll- Rand Co. for use of compressed natural gas (CNG) as automotive fuel. System consists of three separate components- engine conversion equipment; cylinders for storage at 3000 psig in trunk; and the recharging equipment. Cost of conversion (including storage cylinders) is about 450 dollars. Vehicle has a 150 mi range per fill. Estimated cost of CNG, that has a lowest air pollution level, is about 1. 9 cent per mile, against 3. 0 and 3. 2 for LNG and LPG respectively.