GL1200 engine pings until 3K rpm

imported post

check this out for fuel ratings. There are two different ways to measure. The 91 you see is probably the equivalent of 87 pump octane.

taken from http://www.absolut eastronomy.com/topics/Octane_rating

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engineEngine
An engine is a mechanical device that produces some form of output from a given input.An engine whose purpose is to produce kinetic energy output from a fuel is called a Wiktionaryrime mover; alternatively, a motor is a device which produces kinetic energy from a preprocessed "fuel" ....
with a variable compression ratioCompression ratio
The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber; from its largest capacity to its smallest capacity....
under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timingIgnition system
An ignition system is a system for igniting a fuel-air mixture. It is best known in the field of internal combustion engines but also has other applications, e.g....
to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

In most countries (including all of EuropeEurope
Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural , the Caspian Sea, and by the Caucasus Mountains to the southeast....
and AustraliaAustralia
Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
) the "headline" octane rating, shown on the pump, is the RON, but in the United StatesUnited States
The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
, CanadaCanada
Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean....
and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the USUnited States
The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
and CanadaCanada
Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean....
, is 91–92 in Europe. However most European pumps deliver 95 (RON) as "unleaded", equivalent to 90–91 US (R+M)/2, and some even deliver 98 (RON), 100 (RON), or 102 (RON).