Given such a small sample size of people running E85 in their FRS/BRZ and the fact that these cars only been in production for 4yrs, trying to get
definitive PROOF that this particular vehicle application cannot handle longterm use of E85 will not happen for a few more years at the least. I have yet to see a post on this forum of someone who had serious damage from running E85 (that's not to say that there isn't one).
Like @
steve99 stated above "no one can give you a 100% guarantee, but guys have been running e85 for 3 years plus and 100'000 plus miles no issues."
I think that this can be said for many many aftermarket mods, IMHO anyone who is willing to modify their vehicle and stray away from OEM must come to terms with the fact that what they are putting in/on their car might decrease the overall life of their vehicle. Keep in mind I am not one of those OEM purists, I simply deal in logic and accept the fact that when I mod my car it may be detrimental in the long run.
Personally, I started running E85 2 months ago (only about 1k miles so far), I did ponder the risks/reward of doing so and gathered all of the information I could on the subject before making the switch. I will say that the car drives and feels much more responsive and is well worth it, in my current opinion. However, that opinion may change if the motor blew or something was broken/damaged and I had definitive evidence that such damage was caused from running E85.
Whichever way you choose E85 or not, getting an OFT and catless header might have been the best money/mod combo I've ever had on any of my cars. It makes the car feel like it
should have felt from the start.