by Yowie » Sun Feb 27, 2022 6:02 pm
Welcome.
Others can reply Re whether a H6 needs 98 octane. Even if 95 is ok in it, I would run 98 if I owned one.
Don't muck around with E85 (blends or "neat") unless the car is set up for it. At minimum this will be a tune to suit, but could involve bigger injectors, replacement fuel lines, bigger fuel pump, etc.
E85 (being 85% ethanol) contains fewer calories of energy per litre than petrol. As such a greater volume of liquid needs to be injected under most/all running conditions. If your factory computer isn't set up for E85 it will inject a "petrol quantity" of fuel, the car will run lean, knock will probably occur under load (despite the anti-detonation quality of the fuel) and engine damage may result.
Also, if the ECU isn't set up for E85 it won't know to advance the ignition for more power, so the fuel-blending or wrong-fuel-adding exercise is probably pointless from a "more power" point of view. When my turbo forester was tuned for correct E85 fuel volume but NOT ignition timing it made no extra power (I had the car for a few days between tune stages).
If you or a mate try it anyway, get lucky & prove my predictions wrong - well done, but you will be gambling with that engine.
Best wishes for the exciting journey of learning more about your car & power-adding. We all have to start somewhere.