[paulca]

Just an observation, but looking through posts on here it looks like a lot of you US guys are stuck with 91 and 93 RON unleaded.

Totally bizarre. Over here in the UK basic bargain supermarket petrol from the likes of Tesco's or Asda(Walmart) is 95 RON.

BP Ultimate 97 is what I've settled on as it's easily available locally.

Tesco's do "Tesco 99" and Shell do V-Power Nitro 99. I'm not sure I would trust Tesco 99 and there are no shell stations in my area.

BP also do Ultimate 102, but I haven't seen it yet.

The petrol filler has a sticker on it in the UK says something like "98 RON Unleaded only!"

I understand the engine will adjust the timing of course, but with higher octane fuel you apparently get more ignition advance and slightly more power and/or better economy.

Downside, of course, is over here BP Ultimate 97 costs $2.34 a litre, crica $8.86 a US gallon. An average fill up costs me about $90-100.