I had an Equinox that had the flex fuel Ecotech. I tested out the E85 capability a couple of times driving between Phoenix and Las Vegas and for sure saw a drop in mileage. It's been a couple of years so I don't recall the exact numbers, but I think it lost around 100 miles of range on that tank. Based on that there was no way that it was going to be a cheaper alternative, and it might have come close to breaking even with gas when factoring the lower per gallon cost. Taking the cost savings from the equation and all that's left was mileage/range, which was less than gas so I had to stop more often to fuel up.
As for changes in power I could swear it felt a slight bit more peppy when measured with the butt dyno. It wasn't huge, it just seemed like maybe (MAYBE) it was a tad more responsive when passing. My logic was since that motor was 11:1+ that maybe with the extra octane rating of the E85 the pcm could put in more timing. But then again, it could have easily been my imagination.
As for adding the option to the vehicle, I don't know that I would go out of my way to pay for it, but if the car came equipped with it standard I wouldn't turn it down, it adds another fuel option and let's me park in the Fuel Efficient Vehicle spaces at some of my customers facilities.
