by Brian Hitney
21. August 2007 07:10
For more than 15 years I've been standing at the gas pump wondering, "what the heck is the (R+M)/2 method for determining the octane rating?"
I mean, is it really necessary to tell me the formula? Do different gas stations do it differently? Obviously, the sum of two numbers divided by 2 is an average, but what does it mean?
Here's an quote from
csgnetwork:
Gasoline pumps typically post octane numbers as an average of two
different values. Often you may see the octane rating quoted as
(R+M)/2. One value is the research octane number (RON), which is
determined with a test engine running at a low speed of 600 rpm. The
other value is the motor octane number (MON), which is determined with
a test engine running at a higher speed of 900 rpm. If, for example, a
gasoline has an RON of 98 and a MON of 90, then the posted octane
number would be the average of the two values or 94.
There you have it. So in a nutshell, it seems it's a test at slightly different RPMs.
Sources:
http://www.csgnetwork.com/octaneratecalc.htmlhttp://www.havoline.com/carcare/glossary/r.html
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