[M.D. Holloway]

Measuring octane is an interesting thing, actually there are a few different ways:

There is the RON which is the Research Octane Number and its determined by running fuel in a very specialized test engine (one cylinder I believe) - it is able to vary the compression ratio and measure the response for the fuels and compare it to isooctane (an octane of 100) and heptane (and octane of 0) values. These are the standards. The engines ain't cheap and even more costly to maintain. I know a man who travels the country servicing them and he pretty much writes his ticket!

Then there is the MON or Motor Octane Number. This is similar to the RON test but the fuel is heated, the engine RPMS are run higher and they do something with the timing as well all in an attempt to push the fuels anti-knock to the limit. There is no direct link to the RON number and the MON number but the MON can be as much as 10 points lower then the RON. The value we see at the pump is an average of RON and MON which is referred to as the AKI or Anti-knock Index or the PON or Posted Octane Number. Next time your at the pump you may see the equation (R+M)/2, thats what they are referring to.

Did you know methane has a RON and MON of 120? Methanol and ethanol have RONs of 108 but MONs of 89. Isopropanol and xylene have RONS of 118 as well but toluene has a RON of 121.

Those octane booster additives that you buy is nothing more then paint thinner or alcohol!