Octane Ratings

[wolosp]

I've just returned to the UK after a week's training course a few miles outside Boston Mass. I have a Chimaera 4.0 here which requires 98 RON (98 octane) unleaded fuel - known as Super Unleaded in the UK. While I was in the US I saw three types of fuel:
Regular - 85 RON
Super - 87 RON
Supreme - 93 RON.
How do you lot run TVRs on this stuff? Additives? or are we talking about differing methods of calibrating octane ratings here?
Cheers.

[wolosp]

Thanks for that explanation...though I recall the figures quoted on the pumps as RON, anyway I think that clears it up. Thanks again.