> >... the difference being that octane is measured by MON in the USA and
> >RON in the UK. They are not the same thing!
>
> Ah. I had wondered if something like that might be the case. How do
> they compare?

Signature
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')
>See Mike Smith's posting for the correct (and more detailed)
>information!
Thanks - that one hadn't appeared on my server when I wrote my posting
earlier.
Mike refers to an interesting Wikipedia article, from which I quote:
'87 octane fuel, the "normal" gasoline in the US and Canada, would be
91 in Europe'.
So, in spite of the difference in measurement methods, the fuel
available in the US does typically have a lower octane rating than
that here - I can't buy anything as low as 91. The norm here is 95.
Ergo, I still think that motor manufacturers will have to tune their
engines differently for different markets if they're to function
satisfactorily with locally-available fuel.
Does the higher octane rating of British fuel imply that identical
cars would perform better on British fuel than American?
Peter.
Ed Pirrero - 31 May 2006 14:33 GMT
> >See Mike Smith's posting for the correct (and more detailed)
> >information!
[quoted text clipped - 9 lines]
> available in the US does typically have a lower octane rating than
> that here - I can't buy anything as low as 91. The norm here is 95.
No. The effective, in-motor octane number of the fuel is the same,
it's just the measurement method is different.
If I give you 3.785 liters of something, or one U.S. gallon, you still
have the very same volume.
RON numbers are always higher that MON numbers on motor fuels. I know
for a fact that some premium gasolines run 98 RON and 88 MON. I've
seen some regular gasolines at 94 RON and 82 MON. They really can
diverge quite a bit.
The wiki article is interesting, but the 87 in the U.S. = 91 in Europe
is just plain wrong IME.
--
E.P.
'95 UrS6
Peter Bell - 31 May 2006 14:35 GMT
> Does the higher octane rating of British fuel imply that identical
> cars would perform better on British fuel than American?
If the engine is tuned to run on a certain octane rating fuel, then it
will perform less well on a lower octane rating. A higher octane fuel
won't, necessarily, improve the performance.
My RS6 is specified for 98 octane, but with the ability to run on 95
octane with lower performance (as are many recent UK-supplied Audis).
Initially I ran with Super unleaded (97 octane). I started using Shell
Optimax (~98.6 octane) and the fuel consumption showed an immediate 10%
improvement. I have made no measurements of performance, but the car
certainly feels better on Optimax.

Signature
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')
Richard Goulding - 31 May 2006 14:47 GMT
> > Does the higher octane rating of British fuel imply that identical
> > cars would perform better on British fuel than American?
[quoted text clipped - 9 lines]
> improvement. I have made no measurements of performance, but the car
> certainly feels better on Optimax.
My A4 Quattro is specified to run on 98 RON. Recently I have been running it
on 99 RON fuel and it seems to perform even better and it's cheaper than
Optimax.
Have you tried 99 RON fuel ?
Richard
Peter Bell - 31 May 2006 17:14 GMT
> Have you tried 99 RON fuel ?
Unfortunately I'd have to go well out of my way to get to Tesco.

Signature
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')
Mike Smith - 31 May 2006 17:17 GMT
>> See Mike Smith's posting for the correct (and more detailed)
>> information!
[quoted text clipped - 9 lines]
> available in the US does typically have a lower octane rating than
> that here - I can't buy anything as low as 91. The norm here is 95.
95 RON would indeed be higher octane than US 87 AKI (what we call
"regular"), more like 90-91 AKI (what we call "mid-grade"). US
"Premium" tends to be about 93 AKI (i.e. about 98 RON).
> Does the higher octane rating of British fuel imply that identical
> cars would perform better on British fuel than American?
If the car is designed to do so, yes. Otherwise, no.
--
Mike Smith