So I thought I was saved because everybody but Mobile switched to 91 Octane. Well, now they've switched too. Dammit. Will this hurt my FD? Anything to watch out for? (Like no more driving hard on real hot days or something)

 

I run 91 (thats as high as we get up here ) But I run octane booster. The car seems to run just fine with regalar 91 but, I do see knock readings on my Power FC about 20-25 higher than when I'm running booster.

 

Update to this thread. I filled up with Mobile 91 Octane and am running fine. I did some tests yesterday and haven't found any real difference besides a slight "feeling" that I'm a little slower (which is probably just in my head). I doubt you will have the same results with a highly modified car. I have a stock RX7-R1 with no mods except for a straight out after the cat-back.

 

i've used 2 tanks of chevron supreme 91 octane and there have been no ill effects yet. mods below.

 

I used 91 octane for over 53K miles and it was all good as far as I could tell. That is all we get here in OK, except for the few Sinclair and very, very few Texaco stations.

 

I wonder how different grades of fuel affect a FD at extreme high or extreme low altitudes? I know that on a NA engine, lower octane is better at high altitudes. Anybody know about this?