Typical Fuel Selection Switch Installation. Initial fleet test data indicates driver acceptance of vehicle driveability, cold starting, and net vehicle performance. Fuel mileage equivalent to a gallon of gasoline is significantly lower. However, net operating costs compared to gasoline are approximately equal. Other positive indications include reduced oil contamination and decreased engine wear, thus, reduced operational costs result.
Operators are concerned with fuel fill rates.
Early fill systems took up to twelve hours to completely charge the fuel tank. Newer, high-pressure, fast fill systems completely refill a typical tank in five minutes or less, but these systems are more expensive to install. Opponents to CNG warn of potentially costly maintenance for these high pressure, multi-staged pump systems. More analyses and additional testing needs to be completed prior to mass, widespread manufacturing of dedicated CNG vehicles. For the 1993 model year, General Motors and Chrysler have committed to producing at least 2,000 dedicated CNG vehicles.