Came across Lycoming Service Instruction No. 1070AB (dated 4/8/2020), “Specified Fuels for Spark-Ignited Gasoline Aircraft Engine Models” (https://www.lycoming.com/sites/default/files/SI1070AB Specified Fuels.pdf). [Document is technical and irrespective of separate FAA certification considerations.]
Question is this – For automotive fuels that meet Lycoming specs, Table 3 of the document ("Fuels and Fuel Grades Approved for Use in Lycoming Engine Models") includes many of the “O” variety engines, but relatively fewer of the “IO” engines. Is there a particular technical reason for this, is it more about what has actually been tested over the years, something else?
Question is this – For automotive fuels that meet Lycoming specs, Table 3 of the document ("Fuels and Fuel Grades Approved for Use in Lycoming Engine Models") includes many of the “O” variety engines, but relatively fewer of the “IO” engines. Is there a particular technical reason for this, is it more about what has actually been tested over the years, something else?