ARE AVIATION PETROL OCTANE NUMBERS COMPARABLE?
Aviation petrols were all highly leaded and graded using two numbers, with common grades being 80/87, 100/130, and 115/145. The first number is the Aviation rating ( aka Lean Mixture rating ), and the second number is the Supercharge rating ( aka Rich Mixture rating ). In the 1970s a new grade, 100LL ( low lead = 0.53mlTEL/L instead of 1.06mlTEL/L) was introduced to replace the 80/87 and 100/130. Soon after the introduction, there was a spate of plug fouling, and high cylinder head temperatures resulting in cracked cylinder heads. The old 80/87 grade was reintroduced on a limited scale. The Aviation Rating is determined using the automotive Motor Octane test procedure, and then converted to an Aviation Number using a table in the method. Aviation Numbers below 100 are Octane numbers, while numbers above 100 are Performance numbers. There is usually only 1 – 2 Octane units different to the Motor value up to 100, but Performance numbers varies significantly above that eg 110 MON = 128 Pe
