Frequently Asked Questions

What is "Dual Fuel"?

Dual Fuel, also known as “Mixed Fuel”, is defined as the simultaneous combustion of two fuels. In the case of APG’s Dual Fuel Technology, natural gas enters the airflow through the turbocharger to the compression chamber in conjunction with independently fuel-injected OEM diesel fuel to operate the engine. After conversion, the engine is able to operate on either 100% diesel fuel, or alternately, on a mixture of diesel fuel and natural gas. At no time is the engine able to operate on natural gas exclusively.



Is the system approved through EPA and CARB?

Under the new EPA Clean Alternative Fuel Vehicle Engine Conversion Final Rule (April 2011), APG’s Turbocharged Natural Gas® Dual Fuel System has currently received EPA OUL approval on over 450 on-road engine families. These approvals apply to six of the most popular OEM engine models (Cat, Cummings, Detroit Diesel, International, Mack, Volvo). Additionally, APG completed testing and is currently compliant under EPA Memo 1A emission guidelines for off-road applications for over 12 CAT and MTU/DD engines. Finally, APG is completing vehicular emission testing to receive EPA IUL approvals for near-new engine model years, and also CARB approvals to open dual fuel markets in California.


APG’s investment in EPA emissions compliance assures the customer will not be subject to any EPA Clean Air Act anti-tampering violations.



Can APG’s Dual Fuel System operate in California?

If the truck is licensed and plated outside of California, and the base diesel engine is permitted to operate in California in its current diesel configuration, APG’s Dual Fuel System can be installed on the truck and operate in California. APG’s Dual Fuel Technology will NOT make a non-compliant vehicle compliant to CARB’s diesel-only standards.



On which fuel does the engine start?

The engine operates on 100% diesel fuel during initial startup. After certain permissive criteria are satisfied, the APG automatic control system commences Dual Fuel operation. When idling, the engine operates on 100% diesel.



What happens to the engine operation if gas supply is exhausted or lost?

If the natural gas supply is lost or depleted, the APG system automatically changes over from Dual Fuel to diesel-only operation. There is no range anxiety or lost time with an APG Dual Fuel System. When natural gas pressure is restored, the process seamlessly returns back to Dual Fuel operation. Engines with APG’s Dual Fuel System will not run exclusively on natural gas.



Will the introduction of natural gas into the engine affect the horsepower?

Engines converted to APG’s Dual Fuel System will operate with no loss of power or torque.



Does the APG technology change anything on the engine?

APG dual fuel technology does not interfere with the engine integrity or normal governor operation. The conversion technology is designed to allow for in-field retrofit of diesel engines without the need to change or modify the design of the base OEM engine.


Conversion hardware is mounted externally and does not require modification of the base engine. APG’s Dual Fuel technology allows owners the flexibility to return to original diesel operation at any time.



Does APG’s Dual Fuel technology affect the lube oil?

Dedicated natural gas engines require special high-temp oil formulation and maintenance cycles, but APG’s dual fuel system allows the engine to operate with standard diesel engine oil and maintenance schedules.



Why can’t the engine use 100% natural gas?

Dedicated natural gas engines operate at very high temperatures (approximately 650 C), which require high-temp parts and are well above the operating temperatures of a standard diesel engine. To preserve the freedom to operate in either a Dual Fuel or a diesel-only mode, APG’s software carefully monitors and regulates the maximum amount of natural gas needed to operate within OEM temperature and pressure specifications.


APG’s Dual Fuel Technology does not change the compression ignition configuration of the base diesel engine. Natural gas requires a spark ignition configuration unless there is a pilot fuel. In the case of APG’s Dual Fuel System, diesel fuel is always present.



Can I use LPG instead of natural gas?

APG’s Dual Fuel System does not operate on liquefied propane gas (LPG) because the BTU content is too high to efficiently run in a Dual Fuel application.



Will my engine run hotter on Dual Fuel?

The Dual Fuel technology is designed to maintain OEM specifications, including engine coolant, oil, exhaust gas and intake air temperatures. APG’s Dual Fuel System replaces diesel fuel normally consumed by the engine with an equivalent quantity of natural gas. This displacement is relative to the heat value of each fuel. Engine air-fuel ratios during Dual Fuel operation remain largely equivalent to 100% diesel operation, resulting in normal peak exhaust gas temperatures and associated peak engine thermal loads.



What effect will the APG Dual Fuel System have on the durability of my engine?

Operation in Dual Fuel mode has no negative effects on engine wear rates and durability. Engine thermal loads are equivalent to 100%-diesel operation so no excess wear of combustion chamber components (pistons, rings, valves, injectors, etc.) occurs.



What does all this do to manufacturer's warranties?

APG technology does not change the base diesel engine design and warranties the Dual Fuel System components for one year after installation. Industry documentation and regulations cite the following in regard to the effects of an approved aftermarket technology on OEM warranties:


Magnusson-Moss Warranty Act of 1975 says the consumer has the freedom to choose aftermarket parts and upgrades without having the OEM warranty voided.


The Federal Trade Commission (FTC) issued a Consumer Alert in January 2011 confirming that it is in fact illegal to void warranties or deny coverage for the use of an aftermarket part.


Specifically, the EPA Alternate Fuel Conversions final rule published on April 8, 2011 states, “the clean alternative fuel conversion manufacturer would normally be held accountable for fixing problems that occur as the result of conversion” but “the OEM would generally retain any parts or systems that retain their original function following conversion and are unaffected by the conversion.



Are maintenance schedules or engine life affected by installation of dual fuel technology?

General maintenance and service cycles remain the same as the base diesel engine.



What are the economic benefits of operating on Dual Fuel?

Annual fuel savings range from 10% to 40% and will vary according to the respective cost of each of the natural gas fuel source (ie: LNG, CNG, pipeline, well-head). Other economic benefits include competitive advantages such as utilization of sequestered natural gas, low cost of ownership and freedom to hedge against future unknown risks of fuel prices.



Can APG’s Dual Fuel Technology be transferred to another engine?

APG’s Dual Fuel Technology can be easily transferred to another engine within APG’s current list of engine families that are compliant with EPA Memo 1A or EPA CAFC regulations. Once the hardware of the Dual Fuel System is re-installed, APG’s ECU will need to be re-flashed by an APG Certified Installer in order to have the appropriate software installed.


The original engine is able to operate on 100% diesel just as it was before the Dual Fuel upgrade occurred.



Contact APG today to Learn More about APG’s Natural Gas Conversion Technology!

For more detailed information download the full FAQ brochure today.

Turbocharged Natural Gas® Dual Fuel Conversions





American Power Group, Inc.  |  2204 125th Avenue  |  Algona, IA 50511  |  866.994.7697