So from this thread I can be all stock and safely pump four gallons of E85 every tank and make some extra power with no harm?
I don't think anyone will tell you that nothing bad could happen running anything outside of factory approved specs, fuel type, ethanol content, or anything else for that matter.
However,
this thread shows a ~7hp and ~30ft-lb gain running E25 on a stock tune. My personal experience running E30 (blended down to 25% or so) was a noticeable bump in power with no CEL or other obvious problems. That is not to say that nothing bad is or could happen. The stock tune adapts to E15 and the factory threshold or margin appears to be above E15. If you ran E85 on a stock tune I would expect a lean condition CEL. E25 appears to within the threshold of adaptation for the stock tune though. YMMV and know that anything above E15 is not Ford approved. Of course, a custom tune is not factory approved either!
