Ron - Mon ???

[Yamaha 225]

Hi!

I need to know what the difference is on RON and MON gas?

RON - Research Octane Number
MON - Motor Octane Number

In Europe where I live, all types of gas is RON. I considder to buy a motor from US and need to know more about RON-MON numbers.

Is the gas on the pumps in US quoted as MON or RON gas?

At my marina we have 95 unleaded and 98 unleaded. These are RON-figures. Can that fuel be used on american drag engines? The guys here with hi compression runs on special 99 octane (RON) Aspen high quality fuel.

:confused: :confused: :confused:
Erik

[ON THE HUNT]

KABOOM!Research Octane number comes from a mechanical test using LOW engine load at a LOW RPM and ignited by a RETARDED spark.Motor Octane number uses the same fuel but with a HIGH engine load,HIGH RPM and ADVANCED ignition timing.As you can see the Research number is high as you do not run your boat under those conditions.With out knowing if you know how to read plugs or piston domes at minimum I would take 3 points off of the RON rating,5 points if you want some margin for error.What are you considering HIGH compression?

[Yamaha 225]

Thanks alot! Yes you are right, I am in touch with a guy with a highly modifyed Yamaha which he says run on 105 octane. I think it will be impossible to run on marina gas, but would not like to put on too slow (little compression) heads. Nedd to know what the 105 Us octane is in European octane if you know what I mean...

:cool:

[Markus]

The topic of RON vs MON has been discussed here many times before.

The short story is that you subtract the RON number you see on the pump at a European gas station by approximately 5 to get to the (RON+MON)/2 number the same gas would have at a US gas station. (European 98 becomes US 92.5 or 93, European 95 becomes US 90, etc)

For the long story, use the search function of this site and read the gasoline FAQ. I have made a link from my links page. (See below)

[Yamaha 225]

Hi! Thanks alot! you are 100 % sure about the numbers you gave?

Erik:cool:

[Markus]

I called the laboratory at a local refinery as well as the customer service of another oil company, and that is what they both said. (Or they gave me MON that was 10 points lower than RON)

The -5-rule may not hold true for 105 octane race gas or 82 octane Ukrainian gas, but it holds true for the kind of gas you can buy at gas stations in the US and Europe. And it held true for Aspen's alcylate gasoline as well when I checked a few years ago.

[Yamaha 225]

Hi Marcus! Thanks alot! Looks like your 36mm carbs will do a fine job! 'How many hps. in that motor? Please post some pics. of it.

Best Regards
Erik, Norway

[Markus]

Do not know how many HP. Got a Merc 2.5 EFI before I got the carbs perfectly jetted. Now the Yamaha just waits for the Merc to blow up.

[Yamaha 225]

I hope you blow the all!!!!!!!!!!!!!!:D :D