A natural gas vehicle (NGV) is any car, truck, or bus that runs on natural gas instead of gasoline or diesel. The engine works much like a conventional gasoline engine, using spark plugs to ignite a fuel-air mixture, but it burns methane stored onboard in either compressed or liquefied form. NGVs are most common in fleet operations like transit buses, refuse trucks, and long-haul freight, though passenger cars and light-duty trucks exist as well.
CNG vs. LNG: Two Ways to Store the Fuel
Natural gas vehicles use one of two storage methods, and the choice comes down to how far the vehicle needs to travel on a single fill.
Compressed natural gas (CNG) vehicles keep the gas in high-pressure tanks where it remains in gaseous form. This is the more common setup for passenger vehicles, city buses, and delivery trucks that return to a home base each night. The drawback is that gas in this form holds less energy per gallon than gasoline. It takes about 5.66 pounds of CNG to match the energy in a single gallon of gasoline, so tanks tend to be bulkier for the same driving range.
Liquefied natural gas (LNG) solves that problem for vehicles that need more range. Cooling natural gas to roughly negative 260°F turns it into a liquid, which packs more energy into a smaller space. That higher energy density makes LNG well suited for Class 7 and 8 heavy-duty trucks, the 18-wheelers and large freight haulers that travel long distances and need fuel range comparable to diesel.
Engine Configurations
Not every NGV is built the same way under the hood. There are three main configurations:
- Dedicated: The engine runs exclusively on natural gas. These vehicles are optimized for the fuel and generally produce the lowest emissions, but they can only refuel at natural gas stations.
- Bi-fuel: The engine can run on either gasoline or natural gas. The vehicle carries separate fuel tanks, fuel lines, and injection systems for both fuels, and a dashboard switch lets the driver choose which one to use. This gives flexibility in areas where natural gas stations are sparse.
- Dual-fuel: Used primarily in diesel trucks, this setup burns natural gas and diesel simultaneously. The diesel acts as an ignition source for the natural gas, since natural gas doesn’t ignite well under compression alone.
Bi-fuel systems are particularly practical for drivers who want the cost and emissions benefits of natural gas but aren’t ready to rely on it entirely. The vehicle’s electronic control module manages the switch between fuels, adjusting the fuel mixture, ignition timing, and emissions controls automatically.
What’s Under the Hood
A dedicated CNG vehicle shares most of its basic architecture with a gasoline car. It has a standard spark-ignited internal combustion engine, a transmission, a battery for starting and electronics, and an exhaust system with a three-way catalytic converter. The differences are in the fuel pathway.
High-pressure fuel tanks, typically cylindrical and mounted in the trunk or under the bed of a truck, store CNG at around 3,600 psi. From there, the gas passes through a high-pressure regulator that drops the pressure down to the level the engine’s fuel injection system needs. A natural gas fuel filter traps contaminants before they reach the injectors, and a manual shutoff valve lets a mechanic or driver cut the fuel supply entirely when needed. The fuel filler receptacle looks different from a gasoline cap and connects to a specialized nozzle at the fueling station.
Fueling Options
CNG stations come in two basic types. Fast-fill stations work like a conventional gas station: you pull up, connect the nozzle, and fill the tank in a few minutes. These are standard at all public fueling locations. Time-fill stations, by contrast, fill vehicles slowly over several hours, typically overnight. Fleets that return to a central depot each evening often use time-fill because it’s cheaper to operate and puts less stress on compression equipment. Some stations offer both options.
LNG fueling is less widespread and mostly serves commercial trucking corridors. The infrastructure gap is one reason NGVs remain concentrated in fleet applications rather than personal vehicles.
Emissions Compared to Gasoline and Diesel
Natural gas burns cleaner than both gasoline and diesel. On a full lifecycle basis, which accounts for everything from fuel production and transportation to combustion in the engine, CNG vehicles produce about 25% less CO2 than equivalent gasoline cars. The benefits are even more pronounced for trucks and buses: nitrogen oxide emissions drop by around 30%, carbon soot falls by 88%, and CO2 drops by roughly 33% compared to diesel.
That soot reduction is significant. Particulate matter from diesel exhaust is a major contributor to urban air pollution and respiratory illness, so switching a city’s bus fleet to natural gas can meaningfully improve local air quality even if the carbon savings are modest in global terms.
Renewable Natural Gas Changes the Math
The emissions picture shifts dramatically with renewable natural gas (RNG). Instead of being drilled from underground, RNG is captured from decomposing organic waste at landfills, wastewater treatment plants, and dairy farms. Chemically, it’s identical to fossil natural gas and works in the same vehicles without modification.
On a lifecycle basis, RNG can cut greenhouse gas emissions by 95% compared to diesel, approaching a nearly net-zero carbon impact. In some cases, particularly dairy farms where manure lagoons would otherwise release methane directly into the atmosphere, capturing that gas and using it as vehicle fuel actually produces a negative carbon intensity score. The fuel prevents emissions that would have happened anyway while also displacing fossil fuels. A growing number of transit agencies and trucking fleets use RNG specifically to meet sustainability targets.
Fuel Cost Differences
Natural gas has historically been cheaper than gasoline, though the gap fluctuates. As of late 2025, the national average price for CNG is $2.96 per gasoline gallon equivalent (GGE), compared to $3.14 per gallon for regular gasoline. A GGE is the amount of CNG that contains the same energy as one gallon of gasoline, so the comparison is apples to apples.
That per-gallon savings adds up quickly for high-mileage vehicles. A transit bus or refuse truck burning through hundreds of gallons a week sees meaningful cost reductions, which is a major reason fleets have been the primary adopters. For individual drivers, the savings are real but smaller, and they need to be weighed against the higher upfront cost of the vehicle and the inconvenience of finding CNG stations.
Safety and Tank Standards
CNG tanks store fuel at very high pressure, which raises an obvious question about crash safety. Federal Motor Vehicle Safety Standard No. 303 specifically addresses this. It sets strict limits on how much pressure a CNG fuel system can lose during and after a crash, requiring that the high-pressure portion of the system remain essentially intact through a 60-minute observation period following impact.
Natural gas itself has a built-in safety advantage: it’s lighter than air. If a leak occurs, the gas rises and disperses rather than pooling on the ground the way gasoline does. This reduces the risk of fire in many accident scenarios. Every CNG vehicle is required to carry a permanent label near the refueling connection showing its service pressure and directing users to inspection instructions on the fuel container, so first responders and refueling technicians know exactly what they’re dealing with.
Range and Practical Trade-Offs
The biggest practical limitation of NGVs is range. CNG holds about 75% of the energy per gallon compared to gasoline, so a CNG tank the same physical size as a gasoline tank will take you a shorter distance. Manufacturers compensate by using multiple tanks or larger tanks, but this eats into cargo or trunk space. Light-duty CNG vehicles typically get 200 to 250 miles per fill, depending on tank size.
LNG vehicles fare better on range because the liquid form is more energy-dense, making long-haul trucking viable. Still, neither CNG nor LNG matches the convenience of a gasoline or diesel vehicle with fueling stations on every corner. For fleet vehicles with predictable routes and access to dedicated fueling, this isn’t a real obstacle. For personal-vehicle buyers, the limited station network remains the biggest barrier to adoption.