Section II. RECIPROCATING ENGINE FUELS
a. Aviation gasoline (AVGAS) is obtained by adding high-octane components, ethyl liquids and antioxidants to light
fractions of petroleum or products of catylitic cracking.
b. The greatest difference among various grades of AVGAS is in anti-knock quality. However, properties in
addition to knock are closely controlled by specifications so that the gasolines will perform properly.
c. Grade 100/130 aviation gasoline is the only grade available in the Army supply system. The other grades, if
authorized for use, may be procured by local purchase.
d. When necessary, the different grades of aviation gasoline conforming to MIL-G-5572 or ASTM D-910-65T
grades and also those designated by NATO code numbers as listed in table 2-5, may be used as specified in table 2-6
under alternate fuel.
a. Gasolines may be colored for purposes of identification and gasolines containing TEL are required by law to be
b. Grade 80/87 aviation gasoline is red, 100/130 is green, 115/145 is purple and commercial 100LL (low lead)
AVGAS is blue.
(1) A change of color of an aviation gasoline usually indicates contamination with another product or a loss in
fuel quality. A color change can also be caused by a chemical reaction that has weakened the lighter dye component.
This color change in itself may not affect the quality of the fuel.
(2) A color change can also be caused by the preservative in a new hose. Grade 115/145 gasoline that has
been trapped for a short period of time in new hose may appear green. Flushing a small amount of gasoline through the
hose usually removes all traces of color change.
(3) During the period of transition from 115/145 to 100/130 grade as the Army Standard Fuel, there will be a
color change resulting from mixing 115/145 purple with 100/130 green, or 100 LL blue in drums, tanks and transporters.
2-10. Operating Limits.
a. Engine operating limits shall not exceed those prescribed for the fuel grade in use. When operating on mixed
grades of AVGAS the engine operating limits shall be those specified for the lowest grade of fuel in the tank.
b. When using a fuel (or mixture) other than the standard Army fuel 100/130 (or NATO equivalent), the applicable
operator's and maintenance manuals should be referred to for special operational and maintenance procedures, so that
power settings may be revised, commensurate with the grade of fuel in use. When going to a higher grade fuel, the
published power settings or curves will be adhered to for all flight conditions.
c. When changing from one grade of fuel to another, for example, for 100/130 to 115/145, it is not necessary to
drain the aircraft fuel system before adding the new fuel.
d. Motor gasoline should not be used in aircraft engines. Because of the special requirements of aircraft and their
engines, aviation gasolines differ from motor gasolines in distillation characteristics, vapor pressure, and tetraethyl lead
content. Furthermore, dissimilar lead compounds are used in the two types of fuels.
e. No emergency fuels are specified for reciprocating aircraft engines.
a. Tetraethyl lead (TEL) is added to fuel to increase its octane or performance rating.
b. Tricresyl Phosphate (TCP) is added to prevent spark plug fouling. Only those specific piston engine aircraft
showing excessive continuous spark plug lead fouling may be serviced with TCP additive fuels.
(1) TCP is stored and issued under NSN 6810-00-597-5775, supplied in 200 ml (cc) cans, and is a MIL-T-
9188, type III product. Each 200 ml can of type III will treat one 55-gallon drum of aviation gasoline.
Do not use Tricresyl Phosphate, Federal Specification TT-T-656.
The concentration of
phosphorus in TT-T-656 is not correct for use in A VGAS.