Re: Octane again

["Mark Battley" <m.battley@domain.elided>]

Just catching up on a few digests - Scott gave a good overview of RON vs MON
etc, including commenting that

>Australian octane and US
>octane appear to have about as much in common as
>Australian dollars and US dollars -- the spelling. :-)

and

>I'd guess that the Australian figures that John quotes
>are most likely the higher RON figures, not the average.  

Which is correct, and we also use RON in NZ. Initially when we changed to
unleaded (1996) we had two only grades available, 91 and 96 RON, which from
what I could find at the time had a (RON+MON)/2 average of about 86 and 91
respectively. The oil companies (still) have the cheek to call the 91
(R+M)/2 "Premium". Looks more like a regular to me! Apparently the
formulations that are used for the unleaded result in a lower MON, and hence
lower average, than an equivalent RON leaded fuel.

Previously our old leaded super was 96 RON, which was about 93 (R+M)2. This
is why some cars that were happy on 96 RON leaded objected to the 96
unleaded - the RON was the same, but the (R+M)/2 was lower.

As in Aus, more recently some oil companies have introduced 98 RON to
improve the situation with vehicles that need a "premium/high octane" grade
of fuel. I haven't seen any data for (R+M)/2 for this, but presumably it is
similar to our previous leaded 96 RON.

Mark Battley
Auckland, New Zealand.

1973 Alfa Romeo 2000 GT Veloce (fine on 91 (R+M)/2)
1989 Fiat Uno Turbo (okay on 91 (R+M)/2, but it does have a knock sensor,
although I don't think the control system is very sophisticated)
1989 Fiat Croma (marginal on 91 (R+M)/2)
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