I'd been running 93 just thinking that my 10:1 motor wouldnt settle for less but never actually trying 87
I just filled up with it and havent done any testing to see if im getting any knock counts or anything but there hasnt been any sign of any knock at all. sotp doesnt feel any diff. either but ill have to do some testing on both counts to know for sure.
What I did notice is that my egt is WAy down! they arent kidding when they say 93 burns slower! it must be burning right down my primary tubes. The egt has dropped around 150 degrees WOT around peak power and thats a pretty big drop, and just driving around its way way lower, im actually really surprised it was this much.
Im not sure what to make of it, it would seem that the motor is more efficient with the lower octane gas since more of it is burning in the chamber rather than in the pipes.

Just a neat little experiment i did today, interesting to really see the difference of octane firsthand.

 

I talked about too much spark advance hurting power in some other thread. Too much octane is the opposite, Pablo. Acts like not enough initial advance. You can either go down in octane, or use your 93ish and crank up intitial advance until you just see knock counts, then back off degree by degree until knock counts disappear. You should get better power and mileage w/more advance and the higher octane.

Me, I always go w/lowest octane that can run a seemingly ok initial advance. Do the advance-to-knock-count test w/bad gas and lock-in there... Maybe you don't have 10:1??????????