Larry N. said:Many of us grew up in the days of leaded gasoline when the choice at the pump was Regular or Ethyl (HiTest), before the days of unleaded, etc. So regular unleaded will be the lowest octane choice, usually 87 at lower altitudes, and 85 in higher places such as Colorado and Wyoming.
Right. I mean, that's what I would assume someone would mean by "regular unleaded" but then we get to the part about using higher octane voiding warranties, so it makes me wonder if there's another definition of that floating around in another part of the world. I am trying to discern if the poster might have read that "unleaded" fuel was required and that using any other fuel would void the warranty and perhaps conflated "unleaded" as a class of fuels with what most people would think "regular unleaded" was (low octane unleaded gasoline). I would certainly agree that Ford's warranty shouldn't and wouldn't cover any damage related from running aviation fuel, kerosene, pure alcohol, E85, methanol, diesel, or some other type of fuel.
Back in the day before the phase out was complete, though, the question was "regular or unleaded".