Technical Info

This page contains links to information pertinent to our products. There are links to the material safety data sheets of each type of aviation fuel that we sell and there is various information on our products that will educate you on some of the origins, uses and grades of the different aviation fuels.


Avgas Content

Aviation gasoline/avgas is required to be an all hydrocarbon product. That is, its components must be chemicals that contain only carbon and hydrogen atoms. The use of oxygenated, chemicals that include oxygen atoms, compounds such as alcohols or ethers, is not permitted. Only a few select additives are permitted and their use is strictly controlled and limited. The primary ingredient in avgas is isooctane. This is a special component produced in the refining process by specialized equipment. StnaB amounts of isopentane and aromatic (ring) compounds are also used. The isopentane allows the correct volatility to be achieved in the final fuel blend Aromatics are used to improve the rich mixture ratings. However, these aromatics must be limited to achieve other specifications. Grade 80 avgas may also contain straight-run gasoline but this component's lower octane rating makes it unsuitable for higher octane blends. Approved additives include alkyl-lead anti-knock additives. Other additives are also used to then control lead deposit formation. Color dyes are required in most grades for safety identification. Another common, and required, additive includes oxidation inhibitors to improve storage stability and inhibit gum formation. Theses anti-oxidant additives also help prevent lead compound precipitation (separation). Other additives such as corrosion inhibitors, fuel system icing inhibitor and static dissipator additives may also be included by agreement with the user, by the military or by some foreign specifications. All other additives are forbidden.


Crude Oil Yield

A barrel of crude oil (42 US Gallons) will yield slightly more than 44 gallons of finished refinery products. This is due to the reduction in density of many crude components during processing. Here is the break-down from a "typical" barrel of oil.

Finished Motor Gasoline                                             19.5 gallons
Distillate Fuel Oil                                                           8.61 gallons
Jet Fuel                                                                             4.20 gallons
Residual Fuel Oil                                                            2.77 gallons
Petroleum Coke                                                             1.60 gallons
Ashphalt and road oils                                                 1.39 gallons
Liquified Gases                                                                1.43 gallons
Petrochemical feedstocks                                          1.22 gallons
Miscellaneous                                                                  2.98 gallons
Finished Aviation Gasoline                                         0.08 gallons
Kerosene                                                                           0.25 gallons


Volatility & Vapour Pressure

Aviation gasoline must be a fuel that is easily converted from its liquid form to a vapor to allow the formation of a combustible air/fuel mixture. If it is not volatile enough, liquid fuel will wash cylinder walls and pistons causing increased wear and crankcase oil dilution. The fuel is also not distributed well amongst the cylinders in carbureted engines. On the other hand, too light of a fuel can cause vapor lock, increased carburetor icing and excessive venting losses. In specifications for aviation gasoline, distillation ranges are given. These specify at what temperature a certain percentage of a sample is evaporated. Initially, between 10 and 40 percent of the fuel must evaporate by 167 F. The 10% requirement ensures sufficient volatility for cold weather starting while the 40% maximum restrains problems with vapor lock and carburetor icing. A 50%, or mid-point, is specified to ensure the fuel consists in an even mixture of components and not combinations of light and heavy materials only. At the upper end of distillation, 90% of the sample must evaporate by 275 F. This helps ensure that lower volatility components are held in proportion. Lower temperatures could be specified, however, a too restrictive specification could result in lower product availability. The sample must be fully evaporated by 338 F. This precludes the inclusion of very heavy materials that would adversely affect performance and contribute to motor oil dilution. This is also used to check fad samples for contamination by distillate fuel such as diesel or jet fuels. The vapor pressure measures the fuels tendency to form vapors over the liquid fuel. The vapor pressure must be high enough to allow adequate vapor formation for starting However, when an aircraft proceeds to higher altitudes, it is possible to lower the pressure over the liquid fuel to less than the vapor pressure and cause the fuel to vapor off. Avgas must have a vapor pressure of between 5.5 to 7.0 psi. This provides the fuel with adequate vapor pressure for starting while maintaining suitability for high altitude flight.


Aviation Gasoline - The Use of Motor Gas in Aircraft

There has been trend toward using motor gasoline in aircraft engines. Gasoline engines intended for use in aircraft were designed for and should be run on one of the ASTM specified grades of aviation gasoline. Most major engine manufacturers specifically exclude motor gasoline from the approved fuels list. For a number of reasons, the use of motor gasoline in aircraft is NOT recommended. Motor gasoline is manufactured to much looser specifications than that of aviation gasoline. Quality and performance vary widely from refiner to refiner and from location to location. Quality control and quality ensurance in motor gasoline is much less stringent. The risk of contamination is also greater due to less careful handling. Also, many components of motor gasoline, especially detergents and oxygenated fuels, are quite variable in type and proportion and are generally not known or readily detectable. Motor gasoline has a much wider distillation pattern than avgas. This can result in poor fuel distribution, poor anti-knock component distribution, and excessive motor oil dilution. Motor gasoline is generally more volatile than avgas and could lead to increased vapor-off, vapor lock and carburetor icing. The anti-knock properties of motor gasoline are also different. While the octane ratings appear similar in number, the tests are conducted differently and are not comparable. The stability of motor gasoline is also much lower than avgas. It will form "gum" much more readily leading to deposits on fuel system and engine components. This can result in fuel system malfunction, filter clogging, or engine problems such as valve sticking. The presence of aromatic, or ring, hydrocarbons are not limited as they are in avgas. Because of their solvent characteristics, they may present problems to certain aircraft components. The presence of oxygenated compounds is quite common in motor gasoline, can cause compatibility problems with fuel lines, seals, gaskets and fuel tank materials. Oxygenated compounds also increase the tendency of fuel to hold water. Also, many other additive that are permitted in motor gasoline are not permitted in aviation gasoline. Some compounds used to control knock inmotor gasoline can result in more corrosive combustion products. Motor gasoline today is also generally unleaded or of extremely low lead content. This can lead to excessive valve and valve seat wear. One of the most basic issues is safety. The quality of motor gasoline is not an issue in automobile safety. The quality of fuel in aviation is of critical importance to safety. Highest quality fuel can only be ensured through the use of ASTM specification aviation gasoline. The responsibility for the consequences resulting from the use of motor gasoline in aircraft is directly borne by the owner or operator who chooses to do so. The possible risks to safety and to aircraft engines and components are hardly outweighed by economic or availability issues. The use of motor gasoline in aircraft is neither recommended nor wise.


Aviation Gasoline - Content Specifications

The density and heat of combustion of aviation gasoline is specified. However, other specification, such as distillation range, greatly limit any variability in these measurements. The freezing point of the gasoline is specified to prevent the formation of solid hydrocarbons during prolonged cold soak at altitude. The formation of solids would of course jeopardize fuel flow and prevent full fuel availability. Avgas must also be stable in storage and under a variety of conditions. A primary form of deterioration is the formation of "gum" through oxidation and polymerization of fuel molecules. These can deposit on fuel system components and cause serious problems. Therefore gum formation is strictly limited in the specifications. The addition of anti-oxidants is required and results in good to excellent storage stability. The sulfur content of avgas is limited to a very small amount. This is needed because sulfur can cause a deterioration in the anti-knock performance of the lead additive. Sulfur also contributes to corrosion of fuel system and engine components. Fuel corrosiveness is tested by a cooper strip corrosion test. Avgas is also tested for water reaction. In this test, samples of fuel and water are mixed and resulting changes are noted. This is used to detect the presence of high octane, and water soluble components such as alcohols in the fuel. These are not permitted and can be detected by both volume change and phase separation in the test sample.


Aviation Gasoline - History & Development

The history of aviation gasoline, usually referred to as avgas, is as old as the history of powered flight. The earliest gasoline powered engines for aircraft were essentially identical to those used in automobiles or motorcycles. The fuel for these engines was naturally occurring, straight-run gasoline produced simply by distilling crude oils. As the both automobile and aircraft engines developed, the requirements for suitable fuels also developed. The needs of automobile and aircraft engines, while similar, diverged in many areas. The years of World War Two saw avgas reach its peak of development. Many grades of increasingly higher octane were formulated. World War Two also saw the development of gas turbine engines for use in aircraft. The advent of these jet engines froze the further development of aviation gasolines While large amounts are and will be consumed, further development of the fuel is unlikely. Avgas is one of the most complex, rigidly controlled products produced by oil refiners. A great number of physical and chemical properties must be controlled in order to produce a very consistent fuel. While specifications are quite detailed, they also contain a suitability requirement. This eliminates the possibility that some product that meets the "specs" but is not adequate for use in aircraft could be marketed. Refiners are forced to consider whether their product actually meets the intent of the specification not just the test results. Specification for avgas are by necessity quite tight. Unlike other common forms of transportation, occupant safety in avaiation is directly related to continuous power production. Thus, the fuel is a safety critical item and demands care and attrition in its manufacture, distribution and storage. The various specifications have produced excellent quality fuels that perform well in a wide range of environments and applications.


100 Low Lead

Aviation gasoline continued to develop and obtain increasingly higher octane ratings through the end of World War II. Since that time about 6 grades have seen service. The advent of jet engines and the subsequent removal of gasoline powered aircraft from marine and military service, has resulted in reduced grade availability. Two grades are currently available in the United States. Fuel grades are designated by their anti-knock characteristics. Engine knock, which describes explosive detonation of the fuel/air mixture or preignition, can cause severe engine damage and subsequent failure in a short period of time. Anti-knock ratings are expressed as Octane Numbers for those of 100 or less and as Performance Numbers for those ratings above 100. These numbers relate the fuels performance compared to a reference fuel of pure isooctane. Because the anti-knock characteristics are influenced by the air/fuel mixture ratio, ratings are developed for both rich mixture performance and lean mixture performance. Rich mixture settings yield higher octane or performance numbers since the added fuel acts as an internal coolant and suppresses knock, prior to 1975, both numbers were reported as the grade designation but current specifications utilize only the lean mixture rating. Currently, ASTM (American Society for Testing and Materials) specifies three grades - 0,10, and IOOLL (low lead). In practice only lOOLL is widely available. Grade 80 continues to be marketed but its distribution and availability is much more limited. Grade 100 is not now seen. With continuing modernization of the aircraft fleet over time, the demand for grade 80 continues to decline. It is expected that it will eventually reach a point when it is no longer economical to manufacture or use.


Jet Fuel

Jet Fuel comes in a variety of grade designators, here are the common civilian and military grades in use today. Jet-A - a narrow cut kerosene product. This is the standard commercial and general aviation grade available in the United States. It usually contains no additives but may be additized with a anti-icing chemicals. Jet-A1 - is identical to Jet-A with the exception of freeze-point. Used outside the US and is the fuel of choice for long haul flights where the fuel temperature may fall to near the freeze point. Often contains a static dissipator additive. Jet-B - is a wide cut kerosene with lighter gasoline type naphtha components. Used widely in Canada, contains static dissipator and has a very low flash point. JP-4 is a military designation like Jet-B but contains a full additive package including corrosion inhibitor, anti-icing and static dissipator was the primary fuel of the United States Air Force for decades but is being phased out in favor of JP-8. JP-5 is another military fuel. It has a higher flash point (140 F min.) and was designed for use by the USNavy on board aircraft carriers. It contains anti-ice and corrosion inhibitors. JP-8 is like Jet-Al with a full additive package. The USAF plans conversion to this product by the year 2000.