The Benefits of AVgas
For Paramotoring and Powered Paragliding
by Mo Sheldon, April, 2004
To begin with, the issues of which fuel or oil to use is a very controversial topic with strong opinions and few clear cut answers. I will try to show why I and many motor gurus prefer using AVgas over pump gas.
Essentially our two stroke PPG engines are basically glorified lawn mower engines. And countless lawn mower engines have run just fine with whatever gas and oil is put in them. However, all engines will run better and last longer if you take care of them, including using fresh supplies of quality oil and fuel. Considering the amount of horses we get out of PPG engines, tolerances are more critical and reliability is a very real issue. It makes sense to put the highest quality oil and fuels in your flying machines as a cheap way to increase the reliability and durability of your two stroke engine.
Below are a bunch of differences between pump gas and AVgas: AVgas smells a whole lot better than pump gas (you will appreciate this if you inevitably spill it inside your vehicle or on your hands).
- AVgas is refined to a much higher standard than pump gas.
- AVgas is much cleaner than pump gas.
- AVgas tends to burn smoother than pump gas(probably because it is 100 octane)
- AVgas has some lead in it which is a lubricant (two stroke engines burn hotter and that extra lubrication can mean the difference between a running engine and a seized one. Also, with better heat dissipation, the engine running on AVgas may last a whole lot longer
- AVgas is the same whether you buy it in California, Alaska or Arizona. Pump gas is different from city to city and season to season.
- AVgas has a blue tint to it for easy viewing in a clear tank. Pump gas is a clear translucent.
- AVgas has a MUCH longer shelf life of several months compared to several weeks with pump gas.
- AVgas will not gum up if left for a long periods (The gumming of pump gas is from all the additives gone bad. AVgas has none of these additives)
- AVgas is an excellent cleaner.
- AVgas costs a little more than pump gas
- and lastly for those wanting a good energy boost... AVgas tastes a whole lot better than pump gas.
There are a few myths about AVgas that are simply untrue. The first is that a two stroke motor will run hotter with AVgas. If anything, the opposite is the case. The higher octane of AVgas makes the fuel burn slower and more efficiently. Also the lead in AVgas helps to dissipate heat and acts as a lubricant. Another myth about AVgas is that it will foul the plug and fill the engine with lead deposits. Again, this myth is completely unsubstantiated. I personally have run the same plug using AVgas for over 100 hours, and the plug looks perfect. Also, I have found high hour engines run primarily with AVgas tend to be cleaner on the insides compared to engines run with pump gas.
Considering the small difference in price between pump gas and AVgas, and all the numerous benefits in favor of using AVgas, I strongly recommend using AVgas for all two stroke engines.
Airparamo was founded and is operated by Mo Sheldon (also known as Maurice Sheldon). Mo started with PPG's many moons ago in March of 1998. He has thousands of flights and hundreds of hours flying PPG's. Mo ranked 3rd in 2003 the USPPA national competitions among some of the world's best pilots. Mo earned an Advanced Flight Instructor (AFI) certification in 2003 from Aero Sports Connection (ASC), an organization dedication to promoting ultralights. HE earned a Flight Instructor rating from the USPPA in 2005. In addition, Mo was voted as PPG Wing Director in ASC in 2002 and continues to hold this role. He founded and helped to organize AZPPG, Arizona Powered Paragliding, a local association dedicated to PPG in Arizona.
I live in New York and we are now using ETHANOL in our gasoline. I have received mixed advice on the storage of fuel containing this additive.
Ethanol can indeed damage fuel system components. The extent of the risk depends to some degree on the age of your motor. The increasing prevalence of gasoline being oxygenated with ethanol has led manufacturers to change to alcohol resistant materials in all components that come in contact with the fuel, but alcohol can be damaging to metal, rubber and plastic fuel system components in older motors. The problem with storing an ethanol blend is that gasoline oxygenated with alcohol readily takes up water when it is present. The water can condense out of humid air inside the tank. With enough water present, gasoline oxygenated with alcohol will separate into two phases - gasoline on top and a water and alcohol mix at the bottom. This will make engine starting difficult or impossible. It also fosters corrosion in the bottom of the tank. However, if your fuel is dry and your tank is completely full, the risk of water contamination with an ethanol blend should not be significantly higher than with regular gasoline. During storage, you should seal the vent to prevent outside air from entering the tank. Oxygenated gasoline does appear to have a shorter shelf life than gasoline that does not contain alcohol. That makes adding a stabilizer even more important. If gasoline that does not contain ethanol is available in your area, that is what you should put in the tank.
Here's a bit more from a well known importer of Fresh Breeze Paramotors, Chris Bowles:
The Motor is jetted for Avgas use, with a 160 jet. I don't know what gas you are currently using. The CA pumpgas in NOT very suitable. It only has 92 octane and a very large amount of Alcohol as well as METB additives. The low octane and the hot burning additives have a very negative effect on our high compression 2 stroke engines, these additives are designed for automotive 4 stroke engines to increase combustion temperatures in order to produce lowest emissions. Avgas burns much cooler. What I am trying to say is please don't use Pumpgas if at all possible. If you must, the main jet should be changed up one size.
I want to renew the recommendation about staying away from ethanol
enhanced fuel. The ethanol acts as a solvent, trying to wash off the
oil thats in the fuel.
This isn't a problem for cars as they have around 60 lbs of oil
pressure directly at the bearings and no fuel in the crankcase - our
2cycle engines rely on the oil that is mixed in with the fuel and
has to travel around the crank before getting into the cylinder.
The reason I mention this again is a recent rod bearing failure
that was possibly caused by 5% ethanol enhanced fuel. Gas stations in most states are required to note the ethanol content
on the pump.
That brings me back to the advantages of 100 LL that has a huge, 5
year shelf life, burns cool and doesn't clog up fuel systems when it
evaporates. It also doesn't yellow or harden fuel tanks and doesn't
With premium fuel at around $ 3.00 the 100 LL is not much higher.
www.airnav.com has a great section on fuel prices around the
I also want to make a plea for using Castrol TTS oil. When we get
engines to repair or rebuild I can always tell the ones that have
used TTS- they are clean inside, few deposits and rings are not stuck.
By the way MORE oil is not good. 50:1 is fine and if more is used it
will actually lean the fuel/air mixture and will make things run
hotter and create unburnt oil deposits.
What else? Oh yeah wires. On older motors there can be problems over
time where the wires connect to the coil. This has been eliminated
and if your Fresh Breeze Simonini doesn't have the silicone wires
they are not hard to retrofit. Please contact Southern Skies first if
you have a problem, the ppgbiglist isn't the greatest place to get
help for specific problems. We can and will be happy to help.
This is from an Experimental Airplane List and applies to our PPG just as much, if not more. Please avoid Ethanol as much as possible.
It is the worst case scenario for us - 2 stroke premix-with the alcohol (that's what Ethanol is, 200 proof clear alcohol) washing the oil out of the mix and with the inverted engine the oil that is supposed to lube the main and rod bearings runs down into the cylinder. It's like washing your crankshaft with solvent during every flight. We have had several main bearings failures attributed to this situation. Ethanol also makes the engine run hotter and requires richer jetting. I have brought this up many times just wanted to keep pilots aware of this as we keep getting reports about this. Use 100 LL if possible, if you can't then use 93 Octane Hi Test without additives. When switching from Pumpgas to Avgas you must jet much leaner (smaller jet) as it runs so much cooler.
Subject: Kitfox-List: AOPA on ethanol
Ethanol Rampant, Mogas Users Warned
AOPA is warning aircraft owners who normally use automotive fuel purchased off the airport to test the gas for ethanol even if the pump doesn't say there's alcohol in the fuel. The federal government mandate to increase the use of renewable fuels in gasoline blends has prompted some companies to add ethanol without notification and that can be dangerous for aircraft engines.
"While AOPA has successfully prevented ethanol from being blended with avgas, there are limits to what the general aviation industry can do to prevent auto gasoline from being blended," AOPA said on its Web Site In Idaho, pure gasoline is apparently so rare that it's no longer available at some airports. "What I'm hearing from my members is that they cannot find ethanol-free auto gas on airports anywhere," Idaho Aviation Aviation Association Director Ken Jackson said in an email to AVweb. "Their choices now are to switch to 100LL, run contaminated fuel, or hang it up."
The FAA forbids the use of ethanol-blended fuel in regular aircraft. Ethanol-blended fuel can harm rubber fuel bladders, damage hoses, and attract water into the engine encouraging rust. FAA studies have also shown ethanol to cause inaccurate readings on fuel gauges and problems with electric fuel pumps. Premium auto gas in some states has been saved from an ethanol mix too, but that may change due to mandates put on the petroleum companies. Avgas is not suited to many older engines because of its high octane. The salvation for pilots who want or need to use mogas could come from the recreational motorsports sector, which may have the numerical clout to make regulators listen. Many engines used in boats, personal watercraft, ATVs and motorcycles are also harmed by ethanol.
Southern Skies, LLC is a full time USHPA and USPPA Certified Paramotoring Shop and School, near Taylorsville, North Carolina in the Brushy Mountains. Southern Skies has been in business since 1994 and has become the United States distributor for German made Fresh Breeze Paramotors and Swing paragliders. They are devoted to the sport of powered paragliding.
And more from Mo, added July 4, 2008:
I have been using exclusively Avgas for years in my paramotors. I have yet
to have an engine seize and have had very few mechanical problems with
thousands of hours flying and doing many, many tandem flights wit lots of
full or near full throttle for large portions of the flights. Also, not one
of my clients has ever seized an engine using Avgas, On the other hand, I
have repaired about a dozens engines that had burned pump gas. I attribute
this discrepancy to the amazing properties of Avgas. I consider it like
cheap insurance since it adds lots of life to our engines in cooler running
burns, extra lubrication, and a more consistent burn. Besides it smells
great and evaporates quickly, leaving no odor at all. This is particularly
nice if you travel with the paramotor inside your vehicle (I have a van) or
accidentally spill some fuel on your hands or clothing.
Unfortunately AVgas is becoming more difficult to buy as airports tighten
their security. Most smaller and medium sized airports have a self-serve
pump that takes a credit card. This is by far the easiest and quickest way
to fill up. As some airports you can just pull up your vehicle and use the
pump. For others with tighter security measures where you can not just rive
in, you may need to physically carry in your fuel containers and walk to the
self serve pumps. Having a small wagon or carry dolly can make this task
MUCH easier, especially if you need to walk far or have lots of fuel. When
you get Avgas at an airport, you DO NOT need to ask for permission since you
are going to use the fuel in an aircraft (Do GA pilots need to ask
permission to fuel their aircraft? Neither should we!). If you do ask for
permission, there is a good chance you will be told no. I have been hearing
that many airports are now telling people they can not fill their fuel cans
for liability and insurance reasons and turn pilots away.
Be forwarned: Avgas does have a much longer shelf life than pump gas, but
Avgas is extremely sensitive to light (particularly UV rays). If Avgas is
exposed directly sunlight it will quickly break down with the lead
separating from the fuel and settling to the bottom of the container. Store
it in sealed containers in a dark place away from light. Also, like any
fuel, do not store mixed fuel (with oil) for too long as it will loose its
potency and may start to coagulate or do other funky stuff.