Q. How much will my company save?

Dual-Fuel technology replaces 50-80% of your diesel fuel with low cost Natural Gas. The cost saving is driven by the quantity of diesel saved and the price differential between CNG or LNG and diesel. Savings can range from .10 to .30 cents per mile.

Q. How /where can I get Natural Gas for my trucks?

The Dual-Fuel engine can operate on CNG, LNG or Bio-Gas. Natural Gas is widely available. It is the same gas that is supplied to homes and industry via the national grid systems. To supply compressed natural gas (CNG), a compressor station can be installed in most locations. There are also widely available Public stations already in operation. Alternatively, a CNG station can be installed and operated at any private location. Natural gas can also be used in its liquid form (LNG). LNG makes an ideal heavy-duty vehicle fuel due to its relatively high energy density. Also, Bio-gas can be harvested from land-fill waste, sewerage waste, animal waste, biomass or bio-digesters.

Q. How much does it cost?

The cost of a Dual-Fuel installation is dependent upon a number of factors: make and model of vehicle, specification of chassis, type of natural gas (LNG or CNG), range requirements and local cost of labor.

Q. What are the environmental benefits of Dual-Fuel?

Heavy-duty vehicles can save over 9 tons of CO2 annually. This is equivalent to removing 10 cars from the road.

Q. How reliable is the product?

As long as your Dual-Fuel vehicle is well maintained, it can be as reliable as your current diesel truck. A Dual-Fuel engine is a diesel engine that can burn a cleaner and less expensive fuel - Natural Gas. Since the engine’s core diesel components are all retained, full diesel back-up is always available. This makes Dual-Fuel engines more reliable than “dedicated” natural gas engines.

Q. Is there Product Support available?

Dual-Fuel customers are fully supported through a comprehensive offering of diagnostic tools and product manuals. Training, literature, spare parts and warranty are available through participating dealers and directly from Clean Air Power Product Support Representatives.

Q. Is the manufacturer’s warranty affected by installing this technology?

The manufacturer's warranty is not affected by installing the technology. The installation of Dual-Fuel carries its own warranty that covers defects in workmanship and material.

Q. How does Dual-Fuel Technology work?

Dual-Fuel technology enables a heavy-duty diesel engine to operate on a high proportion of natural gas. First, a Dual-Fuel engine is a diesel engine, and is unchanged in its basic thermodynamic operation. However, with Clean Air Power Dual-Fuel, diesel combustion is used only to ignite precisely controlled portions of natural gas and air. This is called a pilot injection. The pilot injection is delivered by the standard, un-modified, diesel injection system fitted to the engine. Once ignited, the gas and air combines to burn rapidly and cleanly. By using diesel pilot ignition and retaining the diesel’s high compression ratio, combustion can be achieved at very lean air-fuel mixture ratios. Known as “lean-burn”, this delivers high efficiency and low NOx emissions. The high compression ratio of the diesel engine can be retained due to the high auto-ignition temperature of methane, the main constituent of natural gas. A diesel engine is the most efficient engine for heavy-duty vehicles. It is significantly more efficient than a spark-ignited engine due to: Higher compression ratio, Very lean-burn combustion, No air throttle to cause additional air pumping work on the engine. The Dual-Fuel engine retains all of these attributes and achieves similar efficiency to the diesel engine – after all, it is still a diesel engine.

Q. Will the engine run hotter on Dual-Fuel?

When used in a diesel engine such as our Dual-Fuel engines, exhaust temperature and overall heat rejection remain the same. When an engine retains the same efficiency as diesel heat rejection remains the same as well. This allows the use of standard, existing, base engine components.

Q. Has it been tested in real world conditions?

Yes. This has been firmly established in real world trials. In the past years, over 2,700 Dual-Fuel™ vehicles have covered >1 billion miles on three continents. Several operators have Dual-Fuel™ vehicles that have run for more than a million miles.

Q. What is the difference between CNG and LNG?

Natural gas, a fossil fuel comprised mostly of methane, is one of the cleanest burning alternative fuels. It can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) to fuel cars and trucks.


Compressed natural gas is usually gas with is taken from the national supply grid (at relatively low pressure) and compressed to 200 to 250 bar (200 to 250 times atmospheric pressure – 3000 to 3500 psi) by a gas compressor.  The gas is still in a gaseous state, but held at these high pressures and contained in a strong, safe and certified pressure vessel; either a storage tank or an on-board fuel tank.

As the gas is compressed, it picks up oil and contaminants from the lubrication within the compressor.  Therefore, this contamination must be reduced as, over time, it can deposit within the injection system, forming hard “lacquers” which affect the performance of the injectors, or lead to failure.  Clean Air Power produces gas filters which remove most of this contaminant.  It is recommended that filtration is used to protect and extend the life of the injection system.  This is no different from the filtration requirements of diesel and gasoline in traditional applications.


The most efficient way to transport gas over distances exceeding approximately 3000km is by ship in a liquefied state.  Hence, a significant and growing proportion of imported gas is coming via LNG tanker vessels.  This is part of a growing global energy economy and represents a safe and secure supply of natural gas from multiple, abundant sources throughout the world

Natural gas, which is mainly methane, is a liquid at minus 162 degrees centigrade. Therefore, a liquefaction plant refrigerates natural gas down to this temperature, whereupon it liquefies.  As it cools, heavier hydrocarbons and impurities liquefy earlier and can be taken off, leaving a pure, clean methane-rich LNG at the end of the process.  The resulting LNG is stored or transported in insulated or cryogenic refrigerated containers to the end users.  This LNG can be either vaporised and fed into the national grid network, or transported as LNG to other users, such as road transport, where it is an ideal road fuel.

As a liquid, LNG has over twice the energy density of CNG and can therefore provide increased vehicle range for a given stored volume.

LNG is a very "dry" and "clean" gas, containing very little oil content.  All pintle-type gas injectors require a certain amount of oil content to lubricate the injector seat metal-to-metal contact to avoid catastrophic wear.  Hence, almost all injectors that operate well on CNG, fail due to accelerated wear when operated on LNG.  Due to the unique and patented design of Clean Air Power's gas injectors, both CNG and LNG source gas can be used. 

Clean Air Power vehicles can store LNG or CNG. The choice of fuel depends on the customer's requirements or preferences. As part of the customer support process, Clean Air Power is happy to advise and assist customers in their selection of the most appropriate gas storage medium. Please contact us at info@cleanairpower.com

Q. Can a Dual-Fuel engine prevent damage from combustion knock?

Combustion knock is the result of auto-ignition of gas-air charge and can be heard as a sharp knocking noise, hence its name. If left unchecked, it can cause damage to the engine. A Dual-Fuel™ engine is tuned to accommodate a wide range of gas properties; nevertheless, poor management of stored gas or issues with gas supply can sometimes lead to ‘knock’.

Dual-Fuel™ engines are fitted with a sensor that returns the engine to normal diesel operation if ‘knock’ is detected. Fundamentally, like any engine, the Dual-Fuel™ needs the right fuel. Correctly supplied and managed, there should be no issue.

Q. Will it shorten engine life?

Research conducted in the USA and jointly published by Caterpillar and Clean Air Power has found that running in Dual-Fuel™ can improve engine life and lengthen oil change intervals. Back-to-back tests were carried out running diesel and Dual-Fuel™ on the same engine. The engine lube-oil was subsequently tested for metal and additive content, indicating sources of engine wear and additive depletion. The tests found less iron content and lower additive depletion in the lube-oil from the Dual-Fuel™ engine.

The conclusion is shown below, with the website address to the US Society of Automobile Engineers (SAE):


Q. Can oil change intervals be lengthened?

In the absence of exhaustive field testing, Clean Air Power does not advocate extended oil change intervals for Dual-Fuel™ engines at this time. However, the evidence suggests that running Dual-Fuel™, could benefit the engine. And it certainly does it no harm.

Q. Are conversions complicated?

No. The system is simple and robust. Fitting the system requires absolutely no change to the internals of the diesel engine and only minor modifications to the air inlet piping and the addition of the Dual-Fuel™ ECU and electrical harness.

Q. What about a gas tank?

Storage tanks (gas containment systems) are fitted to the vehicle. Gas can be stored either as compressed natural gas (CNG) or liquefied natural gas (LNG). CNG is housed in an array of six steel tanks, arranged in two sets of three, attached to the chassis. LNG is stored as a liquid at a temperature of around minus 160°C in a stainless-steel vacuum tank, mounted to the chassis. Components to regulate and filter gas are also fitted, delivering fuel at around 6 bar (90 psi) to the injectors.

Q. Is it safe?

Yes. All gas containment comes with safety systems that include electronic shut-off valves, inertia shut-off valves and manual shut-off valves. Natural gas is safe. It is very difficult to ignite, having a higher ignition temperature than diesel and gasoline and a very narrow flammable air-fuel ratio. Natural gas is much lighter than air too, so it disperses safely in the atmosphere and does not pool to form dangerous invisible vapour clouds – like gasoline and LPG.

Q. Can I use LPG instead of Natural Gas?

No, the octane rating of liquid petroleum gas (LPG) is not sufficient to maintain knock protection.

Q. Is the system approved through EPA and CARB?

All of our commercially available systems are either EPA approved or CARB certified.