Mogas as part of a dual-fuel solution

The GAfuels Blog is written by two private pilots concerned about the future availability of fuels for piston-engine aircraft: Dean Billing, Sisters, Ore., an expert on autogas and ethanol, and Kent Misegades, Cary, N.C., an aerospace engineer and aviation journalist.

On Sept. 20, AOPA Online published an article from the staff of the National Air Transportation Association (NATA) titled “Challenges of a dual-fuel solution”. NATA is the country’s largest trade organization focused on companies providing services to the general aviation community. Reflecting the interests of its major constituents, NATA’s activities are concentrated on turbine-powered aircraft used for commercial purposes as opposed to piston-engine aircraft used in sport aviation. While not explicitly stated in the article, the “dual-fuel solution” that NATA opposes is one consisting of the future unleaded 100-octane replacement to 100LL and a lower octane fuel such as Hjelmco’s 91/96UL or 94UL, a new standard for which is soon to be approved by the ASTM.

The article ignores entirely the existence since the 1980s of a dual-fuel solution that not only can dramatically reduce the use of leaded fuel, but also lower significantly the cost to fly and maintain our aircraft. The second fuel in this “solution” is Mogas, more accurately described as unleaded, ethanol-free 91 octane premium gasoline. It is plentifully available and will remain so as long as we drive gasoline-powered vehicles. Currently there are 3,541 FBOs listed on Airnav providing 100LL. By contrast, there are well over 100,000 gas stations in the U.S. whose fuel is delivered by thousands of gasoline distributors whose trucks probably drive past your local airports regularly. Yes, finding fuel without ethanol can be a problem, but thanks to many other people who need it (boaters, ATVs, snowmobiles, power tools, classic cars/bikes, motorsports, etc.) it can generally be obtained. Besides, as of this writing, it appears that the ethanol industry is set to implode due to the end of tax subsidies and near-unanimity from environmental groups that have finally realized that biofuels from corn is a net-negative for the environment, not only for our pocketbooks.

My colleagues and I have written extensively on the many benefits of a dual-fuel Mogas/100 octane solution.  Our work can be found in the GAFUELS blog of General Aviation News, as well as on our web sites, and  NATA’s article as it appears in AOPA Online includes also a discussion on the costs related to the acquisition and maintenance for each fuel pump and fuel delivery vehicle. Some of the statements appearing in this article do not correspond with our experience operating GA aircraft since the 1970s, so we’ve added our comments below.

Challenges of a dual-fuel solution

By National Air Transportation Association staff

While the introduction of additional grades of fuel was a sound strategy for the reduction of lead use in the automotive industry, there are serious challenges to and concerns with the application of that strategy to aviation. Increased costs, lowered availability, and decreased safety combine to make a dual-fuel solution, or transitional solution, to the issue of lead use in aviation unworkable.

These comments imply a focus on the second fuel being sub-100 octane, e.g. 91/96UL or 94UL, and not Mogas. Mogas however is not a “transitional solution” but has been a legal, safe, affordable fuel for GA for over two decades. It can today power 70%-80% of the piston-engine fleet and essentially 100% of the new LSA fleet.

Consider the benefits of Mogas compared to the second sentence from this article:

  1. Cost – Far lower than 100LL, 91/96UL, and other future aviation-only fuels. Marginally more expensive than what one sees at local gas station. Lower maintenance costs using Mogas due to absence of lead deposits.
  2. Availability – Guaranteed as long as there are gasoline-powered vehicles at over 100,000 gas stations or through thousands of gasoline distributors in every corner of the country.

On Jan. 10, 1973, the Environmental Protection Agency (EPA) required that unleaded fuel for automotive uses be made available by mid-year 1974. This requirement began a process that ended in 1996 when the EPA finalized rules for a complete ban on the use of lead in automotive fuels. The 1973 requirement created a dual availability of leaded and unleaded automotive fuel, a strategy that has been suggested as a solution to reduce the amount of lead used in general aviation. The stark differences between aviation gasoline (avgas) and automotive gasoline usage and distribution, however, make this strategy impossible.

In a dual-grade avgas environment, on-airport fuel service providers, known as fixed base operators (FBOs), would experience significant negative effects in addition to the possible higher cost from supply terminals.

But not for Mogas – costs are driven by the use of Mogas in vehicles, not a relatively small number of airplanes. The cost for Mogas is guaranteed to be lower than Avgas as a result of normal volume production and market pressures.

FBOs currently have storage capabilities for one grade of avgas and would be required, due to the need to segregate different grades of aviation fuel, to construct or purchase additional infrastructure to handle additional unleaded grades.

FBOs actually have 2-3 fuels now: 100LL, Jet-A and often diesel or gasoline for ground vehicles. They already deal with segregation of fuels. Jet-A and 100LL pumps are typically co-located yet fuel contamination is rare.  The cost to acquire small, low-maintenance, self-service Mogas tanks of the 2,000-4,000 gallon capacity is around $50,000, installation included.  These can be financed through AIP or state/local funding and justified on the basis of environmental improvements since every gallon of Mogas burned is one gallon less of a leaded fuel being burned. Mogas’ low cost will rejuvenate sport aviation, the source of future pilots and aircraft owners and a key clientele for maintenance shops, flight schools, hangar leases, etc.

This additional infrastructure would include storage tanks, filtration systems and associated piping, and fuel delivery vehicles. Many existing airport or FBO storage facilities have been designed for current needs and would not have room for additional storage tanks. These facilities would need to be completely redesigned or separate facilities for the new grade of avgas would need to be built.

Simple low-cost, skid-mounted, portable, self-service fueling stations are available from a number of sources. Their low footprint means no substantial site preparation is needed, often not even a concrete pad. The only hookups are 110V power and a phone line or wireless connection. Installation can be performed in just a few days. These systems have been used with great success not only at airports around the country but also in remote locations to support mining, construction, military and other operations. There is no need for additional fuel delivery vehicles as the fuel will be provided by a gasoline distributor.

In addition to infrastructure costs, FBOs also would face additional manpower costs. Unlike its automotive counterparts, aviation fuel and the equipment used to store and handle it must undergo a continuous regimen of quality control testing and inspection. Each storage tank or fuel delivery vehicle must undergo specific daily, monthly, quarterly, and annual inspection to maintain compliance with industry standards. A single tank or fuel delivery vehicle can require up to 214 man-hours or more per year to maintain quality standards.

This last sentence implies that each fuel tank or vehicle requires 35 minutes of fuel-related service each day.  We found this excessive and asked the managers at several typical GA airports here in central North Carolina their opinions.  Here is what they told us:

From Karen McCraw, 5W8 and KHBI:

“No, 35 minutes is much too much.  It only takes a few minutes to do the sump, discard the fuel in the holding tank, write the codes in the binder daily.  I’d say 15 minutes is too much.


From Steve Merritt, KLHZ:

“Properly sumping a truck takes about 15 minutes, each tank about the same, then we stick the tanks for accurate quantity measurement.

2 trucks = 30 minutes

2 tanks = 30 minutes

One hour per day for four tanks if done properly.


The introduction of multiple leaded and unleaded grades of avgas also presents significant operational and safety issues. As airports, supply terminals, and FBOs make business decisions as to whether to carry both grades of fuels, the result could likely be reduced availability of certain grades of avgas at specific airports. This patchwork of fuel availability stands to impose significant burdens on aircraft operators, as those operators eliminate from use airports not carrying the correct grade of fuel.

Since no alternative other than Mogas exists today, it is hard to speculate on the impact that another fuel would have.  Its availability will surely though be driven primarily by economics, which is one of the most important benefits of Mogas.  It is safe, affordable and will be available as long as we drive gasoline-powered cars. A distribution system already exists to truck fuel to gas stations, marinas and vehicle fleets with their own fuel farms. Airports are no more remote than these. Adding Mogas can in no way reduce the availability of any existing or future aviation-only fuel. It is fully conceivable that new providers of Mogas selling through self-service pumps or non-profit fuel clubs will emerge as an alternative to existing suppliers should these not be willing to supply Mogas. Open commerce laws at publicly-funded airports require the freedom for such new fuel providers to set up business.

From an FBO perspective, a leading safety concern is misfueling. Misfueling refers to the delivery of the incorrect grade of fuel, or incorrect quantity, to an aircraft. Misfueling is a serious safety concern and has led to aircraft accidents in the past. The industry has worked hard to eliminate misfueling through the use of selective spouts and aircraft filler ports. The introduction of a second grade of avgas would reintroduce the serious dangers of misfueling. Aircraft requiring lead could be subject to serious engine damage or failure in the event that the aircraft was inadvertently fueled with unleaded avgas.

It seems that the NATA staff members who wrote this are unaware that 40 years ago, during the boom years of GA in America, three or more grades of aviation fuels were offered from the same fueling station. The author pumped such fuel as a teenager at Kentucky Flying Service (Bowman Field, Louisville, Ky.) and fuel contamination was never an issue.  Good training of personnel was the solution. Self-service fueling makes problems even less likely, as pilots have a keen interest in assuring the correct fuel is used in their aircraft. Gas stations have multiple grades of fuel including diesel and misfueling is a rarity even among the general non-flying public.

In summary, although NATA’s concerns are focused on finding a solution for the 20%-30% of piston engine airplanes that currently must use an 100-octane fuel, their arguments against a dual-fuel solution completely ignore two major facts:

  1. 70%-80% of the current piston-engine fleet of aircraft and essentially 100% of new LSA aircraft operate best on unleaded, ethanol-free 91 octane gasoline, aka Mogas.
  2. Mogas is legal and safe, it’s available, affordable and its use will significantly reduce the consumption of leaded aviation fuels.

We urge NATA, the AOPA, the EAA and other aviation organizations to advocate for a dual-fuel solution consisting of Mogas and a 100 octane fuel.


  1. says

    Al, please read my statement again. The dual fuel proposal we have made provides a 100 octane solution, be it with 100LL or a suitable replacement for those who require it. But it also provides for the most suitable fuel for those who don’t, the 70%-80% who are better off for cost and maintenance reasons to burn 91 Octane Mogas, not 100LL. BTW – we dispute the 80% figure that has been stated. From our sources, the percentage burned by those who must have 100 octane is around 50%. A recent study by the EASA confirms this, at least in Germany. If they were to lose their supply of Mogas due to ethanol (which is not used there now), it would approximately double the consumption of 100LL. Adding Mogas should NOT come at the decline in availability of an 100 Octane fuel.

  2. says

    Jack –
    “Finally, the state has mandated ethanol in the mogas and the gas companies aren’t ready to work around that mandate when it is for other than cars.”

    The state of California has no ethanol mandate. CA is not one of the six states that has passed a mandatory ethanol law. If it had, you would have had an exemption for aircraft use just as all mandatory ethanol states have. The CARB has a mandatory oxygenate requirement which is met with ethanol up to 5.7% for some southern counties in the state. As of last year CARB now also allows any terminal to supply E10 that wants to. CARB has no authority to regulate aviation gasoline, especially now that the EPA learned that they had no authority to regulate leaded avgas, although they can curb its use if they can show lead levels above a certain amount in the vicinity of an airport.

    The reason that ethanol is spreading everywhere in CA is the same reason it is spreading everywhere else in the country, the unintended consequences of the federal RFS mandate in EISA 2007. If you want to understand why take a look at

    All liability arguments are a smoke screen. If CPM wants to put mogas in a tank on the airport they have every right to do it. Mogas without ethanol is an FAA approved aviation fuel. The hardest part for CPM would be to find a terminal that still has ethanol free mogas. The only terminal I am aware of in California, is the Imperial terminal, but it is also available at the Las Vegas terminal. Any commercial enterprise on the CPM airport that delivers aviation fuel can order it from any terminal that has it. Finding a trucking company to move it for a reasonable fee will be the hardest part, but it is doable. There are a lot of starving freight lines in this economy.

  3. says

    Al –

    Since when did Kent mention that the dual fuel solution precluded taking 100 LL or the 100 octane solution off the market? This is a classic straw man argument. The whole point of the dual fuel solution is to have 100 octane fuel for those who need it, but also have unleaded fuel for those who need it, especially considering the unleaded fuel is already being produced.

    “The “70%-80% of the current piston-engine fleet of aircraft and essentially 100% of new LSA aircraft” which can use unleaded mogas consume only about 20% of the fuel utilizd by the piston-engine GA fleet. The remaining 20%-30% of the piston-powered GA fleet, predominantly supercharged, consume 80% of the aviation gasoline refined today.”

    I defy you to provide any reliable documentation for that statistic. That stat is more onerous than the one that is usually thrown out, the 70/30 rule, 30% of the GA fleet uses 70% of the 100 octane gasoline. I know this stat has been thrown around for at least 8 years, but I can’t find anyone who knows where it came actually came from.

    At AirVenture for the last two years, GAMA has said in the aviation fuels forums that about 20 – 25%% of the GA fleet is using maybe 60% of the 100 LL.

    As you can see this stat is all over the map, but one thing is for sure the need for 100 LL is declining, both because of the economy and because older high performance piston engine airplanes and are being replaced by turbines by commercial operators.

    “When one considers the GA fleet uses only 0.6% of the total fuel used in the U.S.” It is actually closer to 0.15%. This is another stat that nobody can prove. FAA consistently says 300 million gallons per year but the EIA stats consistently say maybe 200 million gallons per year, if that much. How can they be that far apart? The only thing they both agree upon is that the demand for 100 LL has been continually declining for years.

  4. Al Uhalt says

    Your narrative is good as far as it goes, however, it falls well short of addressing the major problem. You have missed some very important points which, while they do not negate what you have written, actually overwhelm your otherwise very logical argument for the aircraft you have represented. In short, “dual fuel” in NOT the total solution.

    The “70%-80% of the current piston-engine fleet of aircraft and essentially 100% of new LSA aircraft” which can use unleaded mogas consume only about 20% of the fuel utilizd by the piston-engine GA fleet. The remaining 20%-30% of the piston-powered GA fleet, predominantly supercharged, consume 80% of the aviation gasoline refined today. These engines REQUIRE leaded fuel or some yet-to-become-available substitute. In fact, the reduction in lead to 100LL fuel has caused significant problems for many of those aircraft which has been largely overcome by expensive modifications to their engines. Termination of leaded fuel production without a suitable substitute for tetraethyl lead will ground that portion of the fleet resulting in a drop of 80% of the aviation fuel purchased today. When one considers the GA fleet uses only 0.6% of the total fuel used in the U.S. to begin with (and even less in other countries), it hardly seems commercially feasible to produce it at all. This would spell the end of all aviation fuel per se and devastate the aviation industry worldwide.

    In short, “dual fuel” as described in your article is not the total answer. We MUST develop a suitable substitute for leaded fuel BEFORE we even think about taking it off the market. Failure to do that will result in the collapse of piston-powered commercial and much private general/business aviation as we know it today.

  5. says

    Our L.A. area airport, CPM, had a tank for 80 octane. I tried to get the county to put mogas there. It now contains an additional supply of 100LL. Their seemed to be 101 reasons why mogas couldn’t be there. As you mentioned, there was the confusion factor, i.e., someone wanting 100 LL might get mogas. Then there was all kinds of liability issues. Finally, the state has mandated ethanol in the mogas and the gas companies aren’t ready to work around that mandate when it is for other than cars.

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