Join Date: Sep 2008
Location: Honolulu, HI, USA
I thought everyone in USA knew by now.
Euros measure octane differently than we do, and unless translated, their octane requirements don't work in USA.
USA generally uses (R+M)/2 = the average of the Research Octane Number and the Motor Octane Number. Never mind how they are arrived at, the equipment is very expensive.
If you can't use 92 or 92 octane, use the best you can get and be happy with it. M K1300GT ran several years on E90 87 octane, though I don't use it any more. I'd not use octane boosters nor would I mess with whatever formula your local supplier uses. If you really have to, toluene can raise the octane rating, but the risk is yours.
Octane ratings in cold areas vary a bit seasonally, but there's little we can do about that. The reason is that cold gas doesn't evaporate (vaporize) as well, so octane rating goes down in cold times (i.e., gets easier to vaporize).