ASTM D910 standard specification for aviation gasolines
4. General
4.1 This specification, unless otherwise provided, prescribes the required properties of aviation gasoline at the time and place of delivery.

5. Classification
5.1 Five grades of leaded aviation gasoline are provided, known as:
Grade 80
Grade 91
Grade 100
Grade 100LL
Grade 100VLL

NOTE 1 - The above grade names are based on their octane/performance numbers as measured by the now obsolete Test Method D614 (Discontinued 1970). A table for converting octane/performance numbers obtained by Test Method D2700 motor method into aviation ratings was last published in Specification D910-94 in the 1995 Annual Book of ASTM Standards, Vol 05.01.

5.2 Grades 100, 100LL, and 100VLL represent aviation gasolines identical in minimum antiknock quality but differing in maximum lead content and color. The color identifies the difference for engines that have a low tolerance to lead.

NOTE 2 - Listing of, and requirements for, Avgas Grades 91/98, 108/135 and 115/145 appeared in the 1967 version of this specification. U.S. Military Specification MIL-G-5572F, dated January 24, 1978 (withdrawn March 22, 1988), also covers grade 115/145 aviation gasoline, and is available as a research report.

5.3 Although the grade designations show only a single octane rating for each grade, they shall meet a minimum lean mixture motor rating and a minimum rich mixture supercharge rating (see X1.2.2).