The two measures of octane rating are "motor"(or MON) and "research"(or
RON). Of the two, research tends to be the higher of the two, usually by
about 6 points.
In this country, the octane number on the pumps is an average of the
two, sometimes refered to as the "RM/2" or "R+M 2/" number.
Most of the owners manuals, when defining acceptable octane ratings for
fuel, refer to the RON number (my 72 manual actually uses the term RON).
just my $.02 worth
Rick Morrison
72 MGBGT
74 Midget
On Sat, 01 Nov 1997 12:07:40 EST mgbob@juno.com (ROBERT G. HOWARD)
writes:
> The octane measure changed along the way. There are/were two
>measures of Octane. I don't remember the names, but one gave a
>considerably higher "rating" than the other. Naturally, it was the
>higher rating that was posted on the pumps. Some time during the "gas
>crisis" the ratings were averaged, so a given gas has a lower rating
>than it once did. Because of that, you can run lower-rated fuel than
>you might think, yet still feed the engine what it needs. Most MGB
>engines will run just fine on 87.
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