Interesting how your petrol standards differ from Finland. I use only 98 E5, 95 "e10" is the other option but meant for economy cars. contains some more ethanol, max 10%. But there's literally only two options available anywhere. E85 flexfuel is stupidly rare over here so I haven't even bothered (would have to travel 30 miles to fill 'er up) and I highly doubt doing a bit of this a bit of that is a good idea in the long run. Choose one and stick to it and see where it gets ya.
tl;dr We have a ton of jabbering about about massive fuel prices over here, yet I've never seen anything like those octane numbers, different octane measuring standard? Could e95 with 10% octane actually be decent fuel for a v8 flexfuel engine and fuel linings? They market the 98 as "V8" fuel after all.
honestly the best way to know if one is better than the other would be to look at your timing retard. this can be done with a cheap 30$ (over here) obd2 Bluetooth dongle and a phone app like torque for 5$ or even some free ones that show live data.
I pull mine up and on 87&89 I do see a little retarding of timing at interstate speeds just as you tip in the throttle. can't feel it at all but you can see it on the screen.(I believe the ecm settings are super aggressive about it since everyone is going to be running cheap gas in this hybrid version) usually about 5deg, but I've seen a flash as much as 10deg. to test if it was other engine noises from high mileage, I ran good 93 thru it, the highest we easily have access to and only get 1-2 deg at the same speeds.
funny I towed a car on a trailer 2k miles round trip in cheap 87 when I first got it without ever thinking to check it. it was probably pulling a good amount timing, but I see no side effects from it. next time I'll tow with 93 thou. around town, I still run 87 and let it do it's thing.
sadly I don't have a flex fuel version. I have e85 right around the corner.
