Go Natural CNG

Compressed Natural Gas can be used in gasoline engines. Lean-burn engines can achieve higher thermal efficiencies when compared with gasoline engines at the expense of higher NOx and hydrocarbon emissions. Electronically-controlled stoichiometric engines offer the lowest emissions across the board and the highest possible power output, especially when combined with exhaust gas recirculation, turbocharging and intercooling, and three-way catalytic converters, but suffer in terms of heat rejection and fuel consumption. A suitably designed natural gas engine may have a higher output compared with a petrol engine because the octane number of natural gas is higher than that of petrol as this would allow for an engine design with a higher compression ratio.

CNG may be refueled from low-pressure ("slow-fill") or high-pressure ("fast-fill") systems. The difference lies in the cost of the station vs. the refueling time. There are also some implementations to refuel out of a residential gas line during the night. Fueling a vehicle from a home natural gas fuel line is becoming more popular in the United States, especially in California and New York, and tax credits are available for installing the necessary appliance.

In the US, federal tax credits are available for buying a new CNG vehicle. Use of CNG varies from state to state. In California, CNG is used extensively in local city and county fleets, as well as public transportation (city/school buses), and there are 90 public fueling stations in Southern California alone. Although natural gas prices are rising, compressed natural gas is available at 30-60% less than the cost of gasoline, as a rule of thumb, in much of California. Personal use of CNG is a small niche market currently, though with current tax incentives and a growing number of public fueling stations available, it is experiencing unprecedented growth. The state of Utah offers a subsidised statewide network of CNG filling stations at a rate of $0.96/gge, while gasoline is above $4.00/gal. Elsewhere in the nation, retail prices average around $2.50/gge, with home refueling units compressing gas from residential gas lines for approx $1.50/gge. Other than aftermarket conversions, and government used vehicle auctions, the only currently produced CNG vehicle in the US is the Honda Civic GX sedan, which is made in limited numbers and available only in a few states.