Did it say RON ?
Measurement methodsEdit
A US gas station pump offering five different (R+M)/2 octane ratings
Research Octane Number (RON)Edit
The most common type of octane rating worldwide is the Research Octane Number(RON). RON is determined by running the fuel in a test engine with a variablecompression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
Motor Octane Number (MON)Edit
Another type of octane rating, called Motor Octane Number (MON), is determined at 900 rpm engine speed instead of the 600 rpm for RON.[1] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON, but there is no direct link between RON and MON. Pump gasoline specifications typically require both a minimum RON and a minimum MON.[citation needed]
Anti-Knock Index (AKI) or (R+M)/2Edit
In most countries, including Australia, New Zealand and all of those in Europe,[citation needed] the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2). It may also sometimes be called the Posted Octane Number (PON).
Difference between RON, MON, and AKIEdit
Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's Sensitivity,[4] and is not typically published for those countries that use the Anti-Knock Index labelling system.
See the table in the following section for a comparison.
Observed Road Octane Number (RdON)Edit
Another type of octane rating, called Observed Road Octane Number (RdON), is derived from testing gasolines in real world multi-cylinder engines, normally at wide open throttle. It was developed in the 1920s and is still reliable today. The original testing was done in cars on the road but as technology developed the testing was moved to chassis dynamometers with environmental controls to improve consistency.[5]
Also https://www.torquecars.com/articles/fuel-octane-ratings.php
This being very relevant.
Modern RON tests use computerized apparatus and the method has been refined so fuels with a RON greater than 100 can be assessed, but the basic principle remains unchanged.
Abbreviation Definition Notes
RON Research Octane Number UK, Europe, South Africa & Australia
MON Motor Octane Number Motor sport applications. Measured under more severe conditions than RON (higher revs etc). Usually 8-10 units lower than the RON.
RdON Road Octane Number Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada
AKI Ant Knock Index Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada
PON Pump Octane Number Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada
(R + M )/2 Average of RON & MON. Usually 4-5 units lower than the RON. USA, Canada
Octane number, Octane rating or octane Could refer to any of the above, if you can work out which country the article was written in you should be able to work it out.